let # imports
    lib                            = import ../1_lib;
    bootstrapTools_darwin-aarch-64 = import ../4_drv_bootTools_darwin-aarch-64;
    bootstrapTools_darwin-x86-64   = import ../4_drv_bootTools_darwin-x86-64;
in
    { 
        localSystem,
        crossSystem,
        config,
        overlays,
        crossOverlays ? []
    }:
        let
            system = localSystem.system;
            bootstrapTools = if localSystem.isAarch64 then bootstrapTools_darwin-aarch-64 else bootstrapTools_darwin-x86-64;
        in
            "fixme"
            
            # useAppleSDKLibs = localSystem.isAarch64;
            # commonImpureHostDeps = [
            #     "/bin/sh"
            #     "/usr/lib/libSystem.B.dylib"
            #     "/usr/lib/system/libunc.dylib" # This dependency is "hidden", so our scanning code doesn't pick it up
            # ];

            # isFromNixpkgs = pkg: !(isFromBootstrapFiles pkg);
            # isFromBootstrapFiles =
            #     pkg: pkg.passthru.isFromBootstrapFiles or false;
            # isBuiltByNixpkgsCompiler =
            #     pkg: isFromNixpkgs pkg && isFromNixpkgs pkg.stdenv.cc.cc;
            # isBuiltByBootstrapFilesCompiler =
            #     pkg: isFromNixpkgs pkg && isFromBootstrapFiles pkg.stdenv.cc.cc;

            # commonPreHook = ''
            #     export NIX_ENFORCE_NO_NATIVE=''${NIX_ENFORCE_NO_NATIVE-1}
            #     export NIX_ENFORCE_PURITY=''${NIX_ENFORCE_PURITY-1}
            #     export NIX_IGNORE_LD_THROUGH_GCC=1
            #     unset SDKROOT
            # '';

            # stageFun = prevStage:
            #     {
            #         name,
            #         overrides ? (self: super: { }),
            #         extraNativeBuildInputs ? [ ],
            #         extraPreHook ? ""
            #     }:
            #         let
            #             cc = if prevStage.llvmPackages.clang-unwrapped == null
            #                 then
            #                     null
            #                 else
            #                     lib.makeOverridable (import ../../build-support/cc-wrapper) {
            #                         name = "${name}-clang-wrapper";

            #                         nativeTools = false;
            #                         nativeLibc = false;

            #                         expand-response-params = lib.optionalString
            #                         (prevStage.stdenv.hasCC or false && prevStage.stdenv.cc != "/dev/null")
            #                         prevStage.expand-response-params;

            #                         extraPackages = [
            #                         prevStage.llvmPackages.compiler-rt
            #                         ];

            #                         extraBuildCommands =
            #                         let
            #                             inherit (prevStage.llvmPackages) clang-unwrapped compiler-rt release_version;
            #                         in
            #                         ''
            #                             function clangResourceRootIncludePath() {
            #                             clangLib="$1/lib/clang"
            #                             if (( $(ls "$clangLib" | wc -l) > 1 )); then
            #                                 echo "Multiple LLVM versions were found at "$clangLib", but there must only be one used when building the stdenv." >&2
            #                                 exit 1
            #                             fi
            #                             echo "$clangLib/$(ls -1 "$clangLib")/include"
            #                             }

            #                             rsrc="$out/resource-root"
            #                             mkdir "$rsrc"
            #                             ln -s "$(clangResourceRootIncludePath "${clang-unwrapped.lib}")" "$rsrc"
            #                             ln -s "${compiler-rt.out}/lib"   "$rsrc/lib"
            #                             ln -s "${compiler-rt.out}/share" "$rsrc/share"
            #                             echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
            #                         '';

            #                         cc = prevStage.llvmPackages.clang-unwrapped;
            #                         bintools = prevStage.darwin.binutils;

            #                         isClang = true;
            #                         libc = prevStage.darwin.Libsystem;
            #                         inherit (prevStage.llvmPackages) libcxx;

            #                         inherit lib;
            #                         inherit (prevStage) coreutils gnugrep;

            #                         stdenvNoCC = prevStage.ccWrapperStdenv;
            #                         runtimeShell = prevStage.ccWrapperStdenv.shell;
            #                     };

            #             bash = prevStage.bash or bootstrapTools;

            #             thisStdenv = import ../generic {
            #                 name = "${name}-stdenv-darwin";

            #                 buildPlatform = localSystem;
            #                 hostPlatform = localSystem;
            #                 targetPlatform = localSystem;

            #                 inherit config;

            #                 extraBuildInputs = [ prevStage.darwin.CF ];
            #                 extraNativeBuildInputs = extraNativeBuildInputs
            #                 ++ [ prevStage.darwin.apple_sdk.sdkRoot ];

            #                 preHook = lib.optionalString (!isBuiltByNixpkgsCompiler bash) ''
            #                 # Don't patch #!/interpreter because it leads to retained
            #                 # dependencies on the bootstrapTools in the final stdenv.
            #                 dontPatchShebangs=1
            #                 '' + ''
            #                 ${commonPreHook}
            #                 ${extraPreHook}
            #                 '' + lib.optionalString (prevStage.darwin ? locale) ''
            #                 export PATH_LOCALE=${prevStage.darwin.locale}/share/locale
            #                 '';

            #                 shell = bash + "/bin/bash";
            #                 initialPath = [ bash bootstrapTools ];

            #                 fetchurlBoot = import ../../build-support/fetchurl {
            #                 inherit lib;
            #                 stdenvNoCC = prevStage.ccWrapperStdenv or thisStdenv;
            #                 curl = bootstrapTools;
            #                 };

            #                 inherit cc;

            #                 # The stdenvs themselves don't use mkDerivation, so I need to specify this here
            #                 __stdenvImpureHostDeps = commonImpureHostDeps;
            #                 __extraImpureHostDeps = commonImpureHostDeps;

            #                 # Using the bootstrap tools curl for fetchers allows the stdenv bootstrap to avoid
            #                 # having a dependency on curl, allowing curl to be updated without triggering a
            #                 # new stdenv bootstrap on Darwin.
            #                 overrides = self: super: (overrides self super) // {
            #                 fetchurl = thisStdenv.fetchurlBoot;
            #                 fetchpatch = super.fetchpatch.override { inherit (self) fetchurl; };
            #                 fetchgit = super.fetchgit.override {
            #                     git = super.git.override { curl = bootstrapTools; };
            #                 };
            #                 fetchzip = super.fetchzip.override { inherit (self) fetchurl; };
            #                 };
            #             };

            #             in
            #             {
            #             inherit config overlays;
            #             stdenv = thisStdenv;
            #             };
            #         in
            #         assert bootstrapTools.passthru.isFromBootstrapFiles or false;  # sanity check
            #         [
            #         ({}: {
            #             __raw = true;

            #             coreutils = null;
            #             gnugrep = null;

            #             pbzx = null;
            #             cpio = null;

            #             darwin = {
            #             apple_sdk.sdkRoot = null;
            #             binutils = null;
            #             binutils-unwrapped = null;
            #             cctools = null;
            #             print-reexports = null;
            #             rewrite-tbd = null;
            #             sigtool = null;
            #             CF = null;
            #             Libsystem = null;
            #             };

            #             llvmPackages = {
            #             clang-unwrapped = null;
            #             libllvm = null;
            #             libcxx = null;
            #             compiler-rt = null;
            #             };
            #         })

            #         # Create a stage with the bootstrap tools. This will be used to build the subsequent stages and
            #         # build up the standard environment.
            #         #
            #         # Note: Each stage depends only on the the packages in `prevStage`. If a package is not to be
            #         # rebuilt, it should be passed through by inheriting it.
            #         (prevStage: stageFun prevStage {
            #             name = "bootstrap-stage0";

            #             overrides = self: super: {
            #             # We thread stage0's stdenv through under this name so downstream stages
            #             # can use it for wrapping gcc too. This way, downstream stages don't need
            #             # to refer to this stage directly, which violates the principle that each
            #             # stage should only access the stage that came before it.
            #             ccWrapperStdenv = self.stdenv;

            #             bash = bootstrapTools;
            #             coreutils = bootstrapTools;
            #             cpio = bootstrapTools;
            #             gnugrep = bootstrapTools;
            #             pbzx = bootstrapTools;

            #             darwin = super.darwin.overrideScope (selfDarwin: superDarwin: {
            #                 # Prevent CF from being propagated to the initial stdenv. Packages that require it
            #                 # will have to manually add it to their build inputs.
            #                 CF = null;

            #                 binutils-unwrapped = bootstrapTools // {
            #                 version = "boot";
            #                 };

            #                 binutils = super.wrapBintoolsWith {
            #                 name = "bootstrap-stage0-binutils-wrapper";

            #                 nativeTools = false;
            #                 nativeLibc = false;

            #                 expand-response-params = "";
            #                 libc = selfDarwin.Libsystem;

            #                 inherit lib;
            #                 inherit (self) stdenvNoCC coreutils gnugrep;
            #                 runtimeShell = self.stdenvNoCC.shell;

            #                 bintools = selfDarwin.binutils-unwrapped;

            #                 inherit (selfDarwin) postLinkSignHook signingUtils;
            #                 };

            #                 cctools = bootstrapTools // {
            #                 targetPrefix = "";
            #                 version = "boot";
            #                 man = bootstrapTools;
            #                 };

            #                 locale = self.stdenv.mkDerivation {
            #                 name = "bootstrap-stage0-locale";
            #                 buildCommand = ''
            #                     mkdir -p $out/share/locale
            #                 '';
            #                 };

            #                 print-reexports = bootstrapTools;

            #                 rewrite-tbd = bootstrapTools;

            #                 sigtool = bootstrapTools;
            #             } // lib.optionalAttrs (! useAppleSDKLibs) {
            #                 Libsystem = self.stdenv.mkDerivation {
            #                 name = "bootstrap-stage0-Libsystem";
            #                 buildCommand = ''
            #                     mkdir -p $out

            #                     cp -r ${selfDarwin.darwin-stubs}/usr/lib $out/lib
            #                     chmod -R +w $out/lib
            #                     substituteInPlace $out/lib/libSystem.B.tbd --replace /usr/lib/system $out/lib/system

            #                     ln -s libSystem.B.tbd $out/lib/libSystem.tbd

            #                     for name in c dbm dl info m mx poll proc pthread rpcsvc util gcc_s.10.4 gcc_s.10.5; do
            #                     ln -s libSystem.tbd $out/lib/lib$name.tbd
            #                     done

            #                     ln -s ${bootstrapTools}/lib/*.o $out/lib

            #                     ln -s ${bootstrapTools}/lib/libresolv.9.dylib $out/lib
            #                     ln -s libresolv.9.dylib $out/lib/libresolv.dylib

            #                     ln -s ${bootstrapTools}/include-Libsystem $out/include
            #                 '';
            #                 passthru.isFromBootstrapFiles = true;
            #                 };
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 tools = super.llvmPackages.tools.extend (selfTools: _: {
            #                     libclang = self.stdenv.mkDerivation {
            #                     name = "bootstrap-stage0-clang";
            #                     version = "boot";
            #                     outputs = [ "out" "lib" ];
            #                     buildCommand = ''
            #                         mkdir -p $out/lib
            #                         ln -s $out $lib
            #                         ln -s ${bootstrapTools}/bin       $out/bin
            #                         ln -s ${bootstrapTools}/lib/clang $out/lib
            #                         ln -s ${bootstrapTools}/include   $out
            #                     '';
            #                     passthru = {
            #                         isFromBootstrapFiles = true;
            #                         hardeningUnsupportedFlags = [ "fortify3" "zerocallusedregs" ];
            #                     };
            #                     };
            #                     clang-unwrapped = selfTools.libclang;
            #                     libllvm = self.stdenv.mkDerivation {
            #                     name = "bootstrap-stage0-llvm";
            #                     outputs = [ "out" "lib" ];
            #                     buildCommand = ''
            #                         mkdir -p $out/bin $out/lib
            #                         ln -s $out $lib
            #                         ln -s ${bootstrapTools}/bin/strip    $out/bin/llvm-strip
            #                         ln -s ${bootstrapTools}/lib/libLLVM* $out/lib
            #                     '';
            #                     passthru.isFromBootstrapFiles = true;
            #                     };
            #                     llvm = selfTools.libllvm;
            #                 });
            #                 libraries = super.llvmPackages.libraries.extend (_: _: {
            #                     libcxx = self.stdenv.mkDerivation {
            #                     name = "bootstrap-stage0-libcxx";
            #                     buildCommand = ''
            #                         mkdir -p $out/lib $out/include
            #                         ln -s ${bootstrapTools}/lib/libc++.dylib $out/lib
            #                         ln -s ${bootstrapTools}/include/c++      $out/include
            #                     '';
            #                     passthru = {
            #                         isLLVM = true;
            #                         isFromBootstrapFiles = true;
            #                     };
            #                     };
            #                     compiler-rt = self.stdenv.mkDerivation {
            #                     name = "bootstrap-stage0-compiler-rt";
            #                     buildCommand = ''
            #                         mkdir -p $out/lib $out/share
            #                         ln -s ${bootstrapTools}/lib/libclang_rt* $out/lib
            #                         ln -s ${bootstrapTools}/lib/darwin       $out/lib
            #                     '';
            #                     passthru.isFromBootstrapFiles = true;
            #                     };
            #                 });
            #                 in
            #                 { inherit tools libraries; } // tools // libraries
            #             );
            #             };

            #             # The bootstrap tools may use `strip` from cctools, so use a compatible set of flags until LLVM
            #             # is rebuilt, and darwin.binutils can use its implementation instead.
            #             extraPreHook = ''
            #             stripAllFlags=" "    # the cctools "strip" command doesn't know "-s"
            #             stripDebugFlags="-S" # the cctools "strip" command does something odd with "-p"
            #             '';
            #         })

            #         # This stage is primarily responsible for building the linker and setting up versions of
            #         # certain dependencies needed by the rest of the build process. It is necessary to rebuild the
            #         # linker because the `compiler-rt` build process checks the version and attempts to manually
            #         # run `codesign` if it detects a version of `ld64` it considers too old. If that happens, the
            #         # build process will fail for a few different reasons:
            #         #  - sigtool is too old and does not accept the `--sign` argument;
            #         #  - sigtool is new enough to accept the `--sign` argument, but it aborts when it is invoked on a
            #         #    binary that is already signed; or
            #         #  - compiler-rt attempts to invoke `codesign` on x86_64-darwin, but `sigtool` is not currently
            #         #    part of the x86_64-darwin bootstrap tools.
            #         #
            #         # This stage also builds CF and Libsystem to simplify assertions and assumptions for later by
            #         # making sure both packages are present on x86_64-darwin and aarch64-darwin.
            #         (prevStage:
            #             # previous stage0 stdenv:
            #             assert lib.all isFromBootstrapFiles (
            #                 with prevStage; [ bash coreutils cpio gnugrep ] ++ lib.optionals useAppleSDKLibs [ pbzx ]
            #             );

            #             assert lib.all isFromBootstrapFiles (with prevStage.darwin; [
            #             binutils-unwrapped cctools print-reexports rewrite-tbd sigtool
            #             ]);

            #             assert (! useAppleSDKLibs) -> lib.all isFromBootstrapFiles (with prevStage.darwin; [ Libsystem ]);
            #             assert    useAppleSDKLibs  -> lib.all        isFromNixpkgs (with prevStage.darwin; [ Libsystem ]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd xnu ]);
            #             assert (with prevStage.darwin; (! useAppleSDKLibs) -> CF == null);

            #             assert lib.all isFromBootstrapFiles (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm compiler-rt libcxx
            #             ]);

            #             stageFun prevStage {
            #             name = "bootstrap-stage1";

            #             overrides = self: super: {
            #             inherit (prevStage) ccWrapperStdenv
            #                 coreutils gnugrep;

            #             # Use this stage’s CF to build CMake. It’s required but can’t be included in the stdenv.
            #             cmake = self.cmakeMinimal;
            #             cmakeMinimal = super.cmakeMinimal.overrideAttrs (old: {
            #                 buildInputs = old.buildInputs ++ [ self.darwin.CF ];
            #             });

            #             # Disable tests because they use dejagnu, which fails to run.
            #             libffi = super.libffi.override { doCheck = false; };

            #             # Avoid pulling in a full python and its extra dependencies for the llvm/clang builds.
            #             libxml2 = super.libxml2.override { pythonSupport = false; };

            #             ninja = super.ninja.override { };

            #             # Use this stage’s CF to build Python. It’s required but can’t be included in the stdenv.
            #             python3 = self.python3Minimal;
            #             python3Minimal = super.python3Minimal.overrideAttrs (old: {
            #                 buildInputs = old.buildInputs ++ [ self.darwin.CF ];
            #             });

            #             darwin = super.darwin.overrideScope (selfDarwin: superDarwin: {
            #                 apple_sdk = superDarwin.apple_sdk // {
            #                 inherit (prevStage.darwin.apple_sdk) sdkRoot;
            #                 };

            #                 # Use this stage’s CF to build configd. It’s required but can’t be included in the stdenv.
            #                 configd = superDarwin.configd.overrideAttrs (old: {
            #                 buildInputs = old.buildInputs or [ ] ++ [ self.darwin.CF ];
            #                 });

            #                 signingUtils = prevStage.darwin.signingUtils.override {
            #                 inherit (selfDarwin) sigtool;
            #                 };

            #                 postLinkSignHook = prevStage.darwin.postLinkSignHook.override {
            #                 inherit (selfDarwin) sigtool;
            #                 };

            #                 binutils = superDarwin.binutils.override {
            #                 inherit (self) coreutils;
            #                 inherit (selfDarwin) postLinkSignHook signingUtils;

            #                 bintools = selfDarwin.binutils-unwrapped;
            #                 libc = selfDarwin.Libsystem;
            #                 # TODO(@sternenseemann): can this be removed?
            #                 runtimeShell = "${bootstrapTools}/bin/bash";
            #                 };

            #                 binutils-unwrapped = superDarwin.binutils-unwrapped.override {
            #                 inherit (selfDarwin) cctools;
            #                 };

            #                 cctools = selfDarwin.cctools-port;
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 tools = super.llvmPackages.tools.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) clang-unwrapped libclang libllvm llvm;
            #                 });
            #                 libraries = super.llvmPackages.libraries.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) compiler-rt libcxx;
            #                 });
            #                 in
            #                 { inherit tools libraries; inherit (prevStage.llvmPackages) release_version; } // tools // libraries
            #             );
            #             };

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #             prevStage.updateAutotoolsGnuConfigScriptsHook
            #             prevStage.gnu-config
            #             ];

            #             # The bootstrap tools may use `strip` from cctools, so use a compatible set of flags until LLVM
            #             # is rebuilt, and darwin.binutils can use its implementation instead.
            #             extraPreHook = ''
            #             stripAllFlags=" "    # the cctools "strip" command doesn't know "-s"
            #             stripDebugFlags="-S" # the cctools "strip" command does something odd with "-p"

            #             # Don’t assume the ld64 in bootstrap tools supports response files. Only recent versions do.
            #             export NIX_LD_USE_RESPONSE_FILE=0
            #             '';
            #         })

            #         # Build cctools, Python, and sysctl for use by LLVM’s check phase. They must be built in
            #         # their stage to prevent infinite recursions and to make sure the stdenv used to build
            #         # LLVM has the newly built cctools instead of the one from the bootstrap tools.
            #         (prevStage:
            #             # previous stage1 stdenv:
            #             assert lib.all isFromBootstrapFiles (with prevStage; [ coreutils gnugrep ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             autoconf automake bash binutils-unwrapped bison brotli cmake cpio cyrus_sasl db
            #             ed expat flex gettext gmp groff icu libedit libffi libiconv libidn2 libkrb5 libssh2
            #             libtool libunistring libxml2 m4 ncurses nghttp2 ninja openldap openssh openssl
            #             patchutils pbzx perl pkg-config.pkg-config python3 python3Minimal scons serf sqlite
            #             subversion texinfo unzip which xz zlib zstd
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [
            #             binutils-unwrapped cctools locale libtapi print-reexports rewrite-tbd sigtool
            #             ]);
            #             assert (! useAppleSDKLibs) -> lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [ Libsystem configd ]);
            #             assert (! useAppleSDKLibs) -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF ]);
            #             assert    useAppleSDKLibs  -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF Libsystem libobjc]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd xnu ]);

            #             assert lib.all isFromBootstrapFiles (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm compiler-rt libcxx
            #             ]);

            #             assert lib.getVersion prevStage.stdenv.cc.bintools.bintools == "boot";

            #             stageFun prevStage {
            #             name = "bootstrap-stage1-sysctl";

            #             overrides = self: super: {
            #             inherit (prevStage) ccWrapperStdenv
            #                 autoconf automake bash binutils binutils-unwrapped bison brotli cmake cmakeMinimal
            #                 coreutils cpio cyrus_sasl db ed expat flex gettext gmp gnugrep groff icu
            #                 libedit libffi libiconv libidn2 libkrb5 libssh2 libtool libunistring libxml2 m4
            #                 ncurses nghttp2 ninja openldap openssh openssl patchutils pbzx perl pkg-config
            #                 python3Minimal scons sed serf sharutils sqlite subversion texinfo unzip which xz
            #                 zlib zstd;

            #             # Support for the SystemConfiguration framework is required to run the LLVM tests, but trying
            #             # to override python3Minimal does not appear to work.
            #             python3 = (super.python3.override {
            #                 inherit (self) libffi;
            #                 inherit (self.darwin) configd;
            #                 openssl = null;
            #                 readline = null;
            #                 ncurses = null;
            #                 gdbm = null;
            #                 sqlite = null;
            #                 tzdata = null;
            #                 stripConfig = true;
            #                 stripIdlelib = true;
            #                 stripTests = true;
            #                 stripTkinter = true;
            #                 rebuildBytecode = false;
            #                 stripBytecode = true;
            #                 includeSiteCustomize = false;
            #                 enableOptimizations = false;
            #                 enableLTO = false;
            #                 mimetypesSupport = false;
            #             }).overrideAttrs (_: { pname = "python3-minimal-scproxy"; });

            #             darwin = super.darwin.overrideScope (_: superDarwin: {
            #                 inherit (prevStage.darwin)
            #                 CF sdkRoot Libsystem binutils-unwrapped cctools cctools-port configd darwin-stubs dyld
            #                 launchd libclosure libdispatch libobjc locale objc4 postLinkSignHook
            #                 print-reexports rewrite-tbd signingUtils sigtool;

            #                 apple_sdk = superDarwin.apple_sdk // {
            #                 inherit (prevStage.darwin.apple_sdk) sdkRoot;
            #                 };
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 tools = super.llvmPackages.tools.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) clang-unwrapped libclang libllvm llvm;
            #                     clang = prevStage.stdenv.cc;
            #                 });
            #                 libraries = super.llvmPackages.libraries.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) compiler-rt libcxx;
            #                 });
            #                 in
            #                 { inherit tools libraries; inherit (prevStage.llvmPackages) release_version; } // tools // libraries
            #             );
            #             };

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #             prevStage.updateAutotoolsGnuConfigScriptsHook
            #             prevStage.gnu-config
            #             ];

            #             # Until LLVM is rebuilt, assume `strip` is the one from cctools.
            #             extraPreHook = ''
            #             stripAllFlags=" "    # the cctools "strip" command doesn't know "-s"
            #             stripDebugFlags="-S" # the cctools "strip" command does something odd with "-p"
            #             '';
            #         })

            #         # First rebuild of LLVM. While this LLVM is linked to a bunch of junk from the bootstrap tools,
            #         # the libc++ and libc++abi it produces are not. The compiler will be rebuilt in a later stage,
            #         # but those libraries will be used in the final stdenv.
            #         #
            #         # Rebuild coreutils and gnugrep to avoid unwanted references to the bootstrap tools on `PATH`.
            #         (prevStage:
            #             # previous stage-sysctl stdenv:
            #             assert lib.all isFromBootstrapFiles (with prevStage; [ coreutils gnugrep ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             autoconf automake bash binutils-unwrapped bison brotli cmake cpio cyrus_sasl db
            #             ed expat flex gettext gmp groff icu libedit libffi libiconv libidn2 libkrb5 libssh2
            #             libtool libunistring libxml2 m4 ncurses nghttp2 ninja openldap openssh openssl
            #             patchutils pbzx perl pkg-config.pkg-config python3 python3Minimal scons serf sqlite
            #             subversion sysctl.provider texinfo unzip which xz zlib zstd
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [
            #             binutils-unwrapped cctools locale libtapi print-reexports rewrite-tbd sigtool
            #             ]);

            #             assert (! useAppleSDKLibs) -> lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [ Libsystem configd ]);
            #             assert (! useAppleSDKLibs) -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF ]);
            #             assert    useAppleSDKLibs  -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF Libsystem libobjc ]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd xnu ]);

            #             assert lib.all isFromBootstrapFiles (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm compiler-rt libcxx
            #             ]);

            #             assert lib.getVersion prevStage.stdenv.cc.bintools.bintools == lib.getVersion prevStage.darwin.cctools-port;

            #             stageFun prevStage {
            #             name = "bootstrap-stage-xclang";

            #             overrides = self: super: {
            #             inherit (prevStage) ccWrapperStdenv
            #                 autoconf automake bash binutils binutils-unwrapped bison brotli cmake cmakeMinimal
            #                 cpio cyrus_sasl db ed expat flex gettext gmp groff icu libedit libffi libiconv
            #                 libidn2 libkrb5 libssh2 libtool libunistring libxml2 m4 ncurses nghttp2 ninja
            #                 openldap openssh openssl patchutils pbzx perl pkg-config python3 python3Minimal
            #                 scons sed serf sharutils sqlite subversion sysctl texinfo unzip which xz zlib zstd;

            #             # Switch from cctools-port to cctools-llvm now that LLVM has been built.
            #             darwin = super.darwin.overrideScope (_: superDarwin: {
            #                 inherit (prevStage.darwin)
            #                 CF Libsystem configd darwin-stubs dyld launchd libclosure libdispatch libobjc
            #                 locale objc4 postLinkSignHook print-reexports rewrite-tbd signingUtils sigtool;

            #                 apple_sdk = superDarwin.apple_sdk // {
            #                 inherit (prevStage.darwin.apple_sdk) sdkRoot;
            #                 };

            #                 # Avoid building unnecessary Python dependencies due to building LLVM manpages.
            #                 cctools-llvm = superDarwin.cctools-llvm.override { enableManpages = false; };
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 llvmMajor = lib.versions.major super.llvmPackages.release_version;

            #                 # libc++, and libc++abi do not need CoreFoundation. Avoid propagating the CF from prior
            #                 # stages to the final stdenv via rpath by dropping it from `extraBuildInputs`.
            #                 stdenvNoCF = self.stdenv.override {
            #                     extraBuildInputs = [ ];
            #                 };

            #                 libcxxBootstrapStdenv = self.overrideCC stdenvNoCF (self.llvmPackages.clangNoCompilerRtWithLibc.override {
            #                     nixSupport.cc-cflags = [ "-nostdlib" ];
            #                     nixSupport.cc-ldflags = [ "-lSystem" ];
            #                 });

            #                 libraries = super.llvmPackages.libraries.extend (selfLib: superLib: {
            #                     compiler-rt = null;
            #                     libcxx = superLib.libcxx.override ({
            #                     stdenv = libcxxBootstrapStdenv;
            #                     });
            #                 });
            #                 in
            #                 { inherit libraries; } // libraries
            #             );
            #             };

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #             prevStage.updateAutotoolsGnuConfigScriptsHook
            #             prevStage.gnu-config
            #             ];

            #             extraPreHook = ''
            #             stripAllFlags=" "    # the cctools "strip" command doesn't know "-s"
            #             stripDebugFlags="-S" # the cctools "strip" command does something odd with "-p"
            #             '';
            #         })

            #         # This stage rebuilds Libsystem. It also rebuilds bash, which will be needed in later stages
            #         # to use in patched shebangs (e.g., to make sure `icu-config` uses bash from nixpkgs).
            #         (prevStage:
            #             # previous stage-xclang stdenv:
            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             autoconf automake bash binutils-unwrapped bison cmake cmakeMinimal coreutils cpio
            #             cyrus_sasl db ed expat flex gettext gmp gnugrep groff icu libedit libtool m4 ninja
            #             openbsm openldap openpam openssh patchutils pbzx perl pkg-config.pkg-config python3
            #             python3Minimal scons serf sqlite subversion sysctl.provider texinfo unzip which xz
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             brotli libffi libiconv libidn2 libkrb5 libssh2 libunistring libxml2 ncurses
            #             nghttp2 openssl zlib zstd
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [
            #             binutils-unwrapped cctools locale libtapi print-reexports rewrite-tbd sigtool
            #             ]);

            #             assert (! useAppleSDKLibs) -> lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [ Libsystem configd ]);
            #             assert (! useAppleSDKLibs) -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF ]);
            #             assert    useAppleSDKLibs  -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF Libsystem libobjc ]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd libclosure libdispatch xnu ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm
            #             ]);
            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.llvmPackages; [ libcxx ]);
            #             assert prevStage.llvmPackages.compiler-rt == null;

            #             assert lib.getVersion prevStage.stdenv.cc.bintools.bintools == lib.getVersion prevStage.darwin.cctools-port;

            #             stageFun prevStage {

            #             name = "bootstrap-stage2-Libsystem";

            #             overrides = self: super: {
            #             inherit (prevStage) ccWrapperStdenv
            #                 autoconf automake binutils-unwrapped bison brotli cmake cmakeMinimal coreutils
            #                 cpio cyrus_sasl db ed expat flex gettext gmp gnugrep groff icu libedit libffi
            #                 libiconv libidn2 libkrb5 libssh2 libtool libunistring libxml2 m4 ncurses nghttp2
            #                 ninja openbsm openldap openpam openssh openssl patchutils pbzx perl pkg-config
            #                 python3 python3Minimal scons serf sqlite subversion sysctl texinfo unzip which xz
            #                 zlib zstd;

            #             # Bash must be linked against the system CoreFoundation instead of the open-source one.
            #             # Otherwise, there will be a dependency cycle: bash -> CF -> icu -> bash (for icu^dev).
            #             bash = super.bash.overrideAttrs (super: {
            #                 buildInputs = super.buildInputs ++ [ self.darwin.apple_sdk.frameworks.CoreFoundation ];
            #             });

            #             darwin = super.darwin.overrideScope (selfDarwin: superDarwin: {
            #                 inherit (prevStage.darwin)
            #                 CF binutils-unwrapped cctools configd darwin-stubs launchd libobjc libtapi locale
            #                 objc4 print-reexports rewrite-tbd signingUtils sigtool;

            #                 apple_sdk = superDarwin.apple_sdk // {
            #                 inherit (prevStage.darwin.apple_sdk) sdkRoot;
            #                 };
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 tools = super.llvmPackages.tools.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) clang-unwrapped clangNoCompilerRtWithLibc libclang libllvm llvm;
            #                 });

            #                 libraries = super.llvmPackages.libraries.extend (selfLib: superLib: {
            #                     inherit (prevStage.llvmPackages) compiler-rt libcxx;
            #                 });
            #                 in
            #                 { inherit tools libraries; inherit (prevStage.llvmPackages) release_version; } // tools // libraries
            #             );

            #             # Don’t link anything in this stage against CF to prevent propagating CF from prior stages to
            #             # the final stdenv, which happens because of the rpath hook.
            #             stdenv =
            #                 let
            #                 stdenvNoCF = super.stdenv.override {
            #                     extraBuildInputs = [ ];
            #                 };
            #                 in
            #                 self.overrideCC stdenvNoCF (self.llvmPackages.clangNoCompilerRtWithLibc.override {
            #                 inherit (self.llvmPackages) libcxx;
            #                 });
            #             };

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #             prevStage.updateAutotoolsGnuConfigScriptsHook
            #             prevStage.gnu-config
            #             ];

            #             extraPreHook = ''
            #             stripDebugFlags="-S" # llvm-strip does not support "-p" for Mach-O
            #             '';
            #         })

            #         # This stage rebuilds CF, compiler-rt, and the sdkRoot derivation.
            #         #
            #         # CF requires:
            #         # - aarch64-darwin: libobjc (due to being apple_sdk.frameworks.CoreFoundation instead of swift-corefoundation)
            #         # - x86_64-darwin: libiconv libxml2 icu zlib
            #         (prevStage:
            #             # previous stage2-Libsystem stdenv:
            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             autoconf automake binutils-unwrapped bison brotli cmake cmakeMinimal coreutils
            #             cpio cyrus_sasl db ed expat flex gettext gmp gnugrep groff icu libedit libidn2
            #             libkrb5 libssh2 libtool libunistring m4 nghttp2 ninja openbsm openldap openpam openssh
            #             openssl patchutils pbzx perl pkg-config.pkg-config python3 python3Minimal scons serf
            #             sqlite subversion sysctl.provider texinfo unzip which xz zstd
            #             ]);

            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage; [ bash ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             libffi libiconv libxml2 ncurses zlib zstd
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [
            #             binutils-unwrapped cctools locale libtapi print-reexports rewrite-tbd sigtool
            #             ]);

            #             assert (! useAppleSDKLibs) -> lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [ configd ]);
            #             assert (! useAppleSDKLibs) -> lib.all        isBuiltByNixpkgsCompiler (with prevStage.darwin; [ Libsystem ]);
            #             assert (! useAppleSDKLibs) -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF ]);
            #             assert    useAppleSDKLibs  -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF Libsystem libobjc ]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd libclosure libdispatch xnu ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm
            #             ]);
            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.llvmPackages; [ libcxx ]);
            #             assert prevStage.llvmPackages.compiler-rt == null;

            #             assert lib.getVersion prevStage.stdenv.cc.bintools.bintools == lib.getVersion prevStage.darwin.cctools-llvm;

            #             stageFun prevStage {

            #             name = "bootstrap-stage2-CF";

            #             overrides = self: super: {
            #             inherit (prevStage) ccWrapperStdenv
            #                 autoconf automake bash bison brotli cmake cmakeMinimal coreutils cpio
            #                 cyrus_sasl db ed expat flex gettext gmp gnugrep groff libedit libidn2 libkrb5
            #                 libssh2 libtool libunistring m4 ncurses nghttp2 ninja openbsm openldap openpam
            #                 openssh openssl patchutils pbzx perl pkg-config python3 python3Minimal scons serf
            #                 sqlite subversion sysctl texinfo unzip which xz zstd;

            #             # Avoid pulling in a full python and its extra dependencies for the llvm/clang builds.
            #             libxml2 = super.libxml2.override { pythonSupport = false; };

            #             darwin = super.darwin.overrideScope (selfDarwin: superDarwin: {
            #                 inherit (prevStage.darwin)
            #                 Libsystem configd darwin-stubs launchd locale print-reexports rewrite-tbd
            #                 signingUtils sigtool;

            #                 # Rewrap binutils so it uses the rebuilt Libsystem.
            #                 binutils = superDarwin.binutils.override {
            #                 inherit (prevStage) expand-response-params;
            #                 libc = selfDarwin.Libsystem;
            #                 } // {
            #                 passthru = { inherit (prevStage.bintools.passthru) isFromBootstrapFiles; };
            #                 };

            #                 # Avoid building unnecessary Python dependencies due to building LLVM manpages.
            #                 cctools-llvm = superDarwin.cctools-llvm.override { enableManpages = false; };
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 tools = super.llvmPackages.tools.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) clang-unwrapped clangNoCompilerRtWithLibc libclang libllvm llvm;
            #                     clang = prevStage.stdenv.cc;
            #                 });

            #                 libraries = super.llvmPackages.libraries.extend (selfLib: superLib: {
            #                     inherit (prevStage.llvmPackages) libcxx;

            #                     # Make sure compiler-rt is linked against the CF from this stage, which can be
            #                     # propagated to the final stdenv. CF is required by ASAN.
            #                     compiler-rt = superLib.compiler-rt.override ({
            #                     inherit (self.llvmPackages) libllvm;
            #                     stdenv = self.stdenv.override {
            #                         extraBuildInputs = [ self.darwin.CF ];
            #                     };
            #                     });
            #                 });
            #                 in
            #                 { inherit tools libraries; inherit (prevStage.llvmPackages) release_version; } // tools // libraries
            #             );

            #             # Don’t link anything in this stage against CF to prevent propagating CF from prior stages to
            #             # the final stdenv, which happens because of the rpath hook. Also don’t use a stdenv with
            #             # compiler-rt because it needs to be built in this stage.
            #             stdenv =
            #                 let
            #                 stdenvNoCF = super.stdenv.override {
            #                     extraBuildInputs = [ ];
            #                 };
            #                 in
            #                 self.overrideCC stdenvNoCF (self.llvmPackages.clangNoCompilerRtWithLibc.override {
            #                 inherit (self.llvmPackages) libcxx;

            #                 # Make sure the stdenv is using the Libsystem that will be propagated to the final stdenv.
            #                 libc = self.darwin.Libsystem;
            #                 bintools = self.llvmPackages.clangNoCompilerRtWithLibc.bintools.override {
            #                     libc = self.darwin.Libsystem;
            #                 };
            #                 });
            #             };

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #             prevStage.updateAutotoolsGnuConfigScriptsHook
            #             prevStage.gnu-config
            #             ];

            #             extraPreHook = ''
            #             stripDebugFlags="-S" # llvm-strip does not support "-p" for Mach-O
            #             '';
            #         })

            #         # Rebuild LLVM with LLVM. This stage also rebuilds certain dependencies needed by LLVM.
            #         #
            #         # LLVM requires: libcxx libffi libiconv libxml2 ncurses zlib
            #         (prevStage:
            #             # previous stage2-CF stdenv:
            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             autoconf automake bison brotli cmake cmakeMinimal coreutils cpio cyrus_sasl
            #             db ed expat flex gettext gmp gnugrep groff libedit libidn2 libkrb5 libssh2 libtool
            #             libunistring m4 ncurses nghttp2 ninja openbsm openldap openpam openssh openssl
            #             patchutils pbzx perl pkg-config.pkg-config python3 python3Minimal scons serf sqlite
            #             subversion sysctl.provider texinfo unzip which xz zstd
            #             ]);
            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage; [
            #             bash binutils-unwrapped icu libffi libiconv libxml2 zlib
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [
            #             locale print-reexports rewrite-tbd sigtool
            #             ]);
            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.darwin; [
            #             binutils-unwrapped cctools libtapi
            #             ]);

            #             assert (! useAppleSDKLibs) -> lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [ configd ]);
            #             assert (! useAppleSDKLibs) -> lib.all        isBuiltByNixpkgsCompiler (with prevStage.darwin; [ Libsystem ]);
            #             assert (! useAppleSDKLibs) -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF ]);
            #             assert    useAppleSDKLibs  -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF Libsystem libobjc ]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd libclosure libdispatch xnu ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm
            #             ]);
            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.llvmPackages; [ libcxx ]);

            #             assert lib.getVersion prevStage.stdenv.cc.bintools.bintools == lib.getVersion prevStage.darwin.cctools-llvm;

            #             stageFun prevStage {

            #             name = "bootstrap-stage3";

            #             overrides = self: super: {
            #             inherit (prevStage) ccWrapperStdenv
            #                 autoconf automake bash binutils binutils-unwrapped bison brotli cmake cmakeMinimal
            #                 coreutils cpio cyrus_sasl db ed expat flex gettext gmp gnugrep groff libedit
            #                 libidn2 libkrb5 libssh2 libtool libunistring m4 nghttp2 ninja openbsm openldap
            #                 openpam openssh openssl patchutils pbzx perl pkg-config python3 python3Minimal scons
            #                 sed serf sharutils sqlite subversion sysctl texinfo unzip which xz zstd

            #                 # CF dependencies - don’t rebuild them.
            #                 icu libiconv libxml2 zlib;

            #             # Disable tests because they use dejagnu, which fails to run.
            #             libffi = super.libffi.override { doCheck = false; };

            #             darwin = super.darwin.overrideScope (selfDarwin: superDarwin: {
            #                 inherit (prevStage.darwin)
            #                 CF Libsystem binutils binutils-unwrapped cctools cctools-llvm cctools-port configd
            #                 darwin-stubs dyld launchd libclosure libdispatch libobjc libtapi locale objc4
            #                 postLinkSignHook print-reexports rewrite-tbd signingUtils sigtool;

            #                 apple_sdk = superDarwin.apple_sdk // {
            #                 inherit (prevStage.darwin.apple_sdk) sdkRoot;
            #                 };
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 libraries = super.llvmPackages.libraries.extend (_: _: {
            #                 inherit (prevStage.llvmPackages) compiler-rt libcxx;
            #                 });
            #                 in
            #                 { inherit libraries; } // libraries
            #             );
            #             };

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #             prevStage.updateAutotoolsGnuConfigScriptsHook
            #             prevStage.gnu-config
            #             ];

            #             extraPreHook = ''
            #             stripDebugFlags="-S" # llvm-strip does not support "-p" for Mach-O
            #             '';
            #         })

            #         # Construct a standard environment with the new clang. Also use the new compiler to rebuild
            #         # everything that will be part of the final stdenv and isn’t required by it, CF, or Libsystem.
            #         (prevStage:
            #             # previous stage3 stdenv:
            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             autoconf automake bison brotli cmake cmakeMinimal coreutils cpio cyrus_sasl
            #             db ed expat flex gettext gmp gnugrep groff libedit libidn2 libkrb5 libssh2 libtool
            #             libunistring m4 nghttp2 ninja openbsm openldap openpam openssh openssl patchutils pbzx
            #             perl pkg-config.pkg-config python3 python3Minimal scons serf sqlite subversion
            #             sysctl.provider texinfo unzip which xz zstd
            #             ]);

            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage; [
            #             bash binutils-unwrapped icu libffi libiconv libxml2 zlib
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [
            #             locale print-reexports rewrite-tbd sigtool
            #             ]);
            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.darwin; [
            #             binutils-unwrapped cctools libtapi
            #             ]);

            #             assert (! useAppleSDKLibs) -> lib.all isBuiltByBootstrapFilesCompiler (with prevStage.darwin; [ configd ]);
            #             assert (! useAppleSDKLibs) -> lib.all        isBuiltByNixpkgsCompiler (with prevStage.darwin; [ Libsystem ]);
            #             assert (! useAppleSDKLibs) -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF ]);
            #             assert    useAppleSDKLibs  -> lib.all                   isFromNixpkgs (with prevStage.darwin; [ CF Libsystem libobjc ]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd libclosure libdispatch xnu ]);

            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm compiler-rt libcxx
            #             ]);

            #             assert lib.getVersion prevStage.stdenv.cc.bintools.bintools == lib.getVersion prevStage.darwin.cctools-llvm;

            #             stageFun prevStage {

            #             name = "bootstrap-stage4";

            #             overrides = self: super: {
            #             inherit (prevStage) ccWrapperStdenv
            #                 autoconf automake bash bison cmake cmakeMinimal cyrus_sasl db expat flex groff
            #                 libedit libtool m4 ninja openldap openssh patchutils perl pkg-config python3 scons
            #                 serf sqlite subversion sysctl texinfo unzip which

            #                 # CF dependencies - don’t rebuild them.
            #                 icu

            #                 # LLVM dependencies - don’t rebuild them.
            #                 libffi libiconv libxml2 ncurses zlib;

            #             darwin = super.darwin.overrideScope (selfDarwin: superDarwin: {
            #                 inherit (prevStage.darwin) dyld CF Libsystem darwin-stubs
            #                 # CF dependencies - don’t rebuild them.
            #                 libobjc objc4;

            #                 apple_sdk = superDarwin.apple_sdk // {
            #                 inherit (prevStage.darwin.apple_sdk) sdkRoot;
            #                 };

            #                 signingUtils = superDarwin.signingUtils.override {
            #                 inherit (selfDarwin) sigtool;
            #                 };

            #                 binutils = superDarwin.binutils.override {
            #                 inherit (prevStage) expand-response-params;

            #                 bintools = selfDarwin.binutils-unwrapped;
            #                 libc = selfDarwin.Libsystem;
            #                 };

            #                 # cctools needs to build the LLVM man pages, which requires sphinx. Sphinx
            #                 # has hatch-vcs as a transitive dependency, which pulls in git (and curl).
            #                 # Disabling the tests for hatch-vcs allows the stdenv bootstrap to avoid having
            #                 # any dependency on curl other than the one provided in the bootstrap tools.
            #                 cctools-llvm = superDarwin.cctools-llvm.override (old: {
            #                 llvmPackages =
            #                     let
            #                     tools = old.llvmPackages.tools.extend (_: superTools: {
            #                         llvm-manpages = superTools.llvm-manpages.override {
            #                         python3Packages = prevStage.python3Packages.overrideScope (_: superPython: {
            #                             hatch-vcs = (superPython.hatch-vcs.override {
            #                             git = null;
            #                             pytestCheckHook = null;
            #                             });
            #                         });
            #                         };
            #                     });
            #                     inherit (old.llvmPackages) libraries release_version;
            #                     in
            #                     { inherit tools libraries release_version; } // tools // libraries;
            #                 });
            #             });

            #             llvmPackages = super.llvmPackages // (
            #                 let
            #                 tools = super.llvmPackages.tools.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) clang-unwrapped libclang libllvm llvm;
            #                     libcxxClang = lib.makeOverridable (import ../../build-support/cc-wrapper) {
            #                     nativeTools = false;
            #                     nativeLibc = false;

            #                     inherit (prevStage) expand-response-params;

            #                     extraPackages = [
            #                         self.llvmPackages.compiler-rt
            #                     ];

            #                     extraBuildCommands =
            #                         let
            #                         inherit (self.llvmPackages) clang-unwrapped compiler-rt release_version;

            #                         # Clang 16+ uses only the major version in resource-root, but older versions use the complete one.
            #                         clangResourceRootIncludePath = clangLib: clangRelease:
            #                             let
            #                             clangVersion =
            #                                 if lib.versionAtLeast clangRelease "16"
            #                                 then lib.versions.major clangRelease
            #                                 else clangRelease;
            #                             in
            #                             "${clangLib}/lib/clang/${clangVersion}/include";
            #                         in
            #                         ''
            #                         rsrc="$out/resource-root"
            #                         mkdir "$rsrc"
            #                         ln -s "${clangResourceRootIncludePath clang-unwrapped.lib release_version}" "$rsrc"
            #                         ln -s "${compiler-rt.out}/lib"   "$rsrc/lib"
            #                         ln -s "${compiler-rt.out}/share" "$rsrc/share"
            #                         echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
            #                         '';

            #                     cc = self.llvmPackages.clang-unwrapped;
            #                     bintools = self.darwin.binutils;

            #                     isClang = true;
            #                     libc = self.darwin.Libsystem;
            #                     inherit (self.llvmPackages) libcxx;

            #                     inherit lib;
            #                     inherit (self) stdenvNoCC coreutils gnugrep runtimeShell;
            #                     };
            #                 });
            #                 libraries = super.llvmPackages.libraries.extend (_: _:{
            #                     inherit (prevStage.llvmPackages) compiler-rt libcxx;
            #                 });
            #                 in
            #                 { inherit tools libraries; } // tools // libraries
            #             );
            #             };

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #             prevStage.updateAutotoolsGnuConfigScriptsHook
            #             prevStage.gnu-config
            #             ];

            #             extraPreHook = ''
            #             stripDebugFlags="-S" # llvm-strip does not support "-p" for Mach-O
            #             '';
            #         })

            #         # Construct the final stdenv. The version of LLVM provided should match the one defined in
            #         # `all-packages.nix` for Darwin. Nothing should depend on the bootstrap tools or originate from
            #         # the bootstrap tools.
            #         #
            #         # When updating the Darwin stdenv, make sure that the result has no dependency (`nix-store -qR`)
            #         # on `bootstrapTools` or the binutils built in stage 1.
            #         (prevStage:
            #             # previous stage4 stdenv:
            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage; [
            #             bash binutils-unwrapped brotli bzip2 cpio diffutils ed file findutils gawk
            #             gettext gmp gnugrep gnumake gnused gnutar gzip icu libffi libiconv libidn2 libkrb5
            #             libssh2 libunistring libxml2 libyaml ncurses nghttp2 openbsm openpam openssl patch
            #             pbzx pcre python3Minimal xar xz zlib zstd
            #             ]);

            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.darwin; [
            #             binutils-unwrapped cctools libtapi locale print-reexports rewrite-tbd sigtool
            #             ]);

            #             assert (! useAppleSDKLibs) -> lib.all isBuiltByNixpkgsCompiler (with prevStage.darwin; [ Libsystem configd ]);
            #             assert (! useAppleSDKLibs) -> lib.all            isFromNixpkgs (with prevStage.darwin; [ CF ]);
            #             assert    useAppleSDKLibs  -> lib.all            isFromNixpkgs (with prevStage.darwin; [ CF Libsystem libobjc ]);
            #             assert lib.all isFromNixpkgs (with prevStage.darwin; [ dyld launchd libclosure libdispatch xnu ]);

            #             assert lib.all isBuiltByNixpkgsCompiler (with prevStage.llvmPackages; [
            #             clang-unwrapped libclang libllvm llvm compiler-rt libcxx
            #             ]);

            #             assert lib.all isBuiltByBootstrapFilesCompiler (with prevStage; [
            #             autoconf automake bison cmake cmakeMinimal cyrus_sasl db expat flex groff libedit
            #             libtool m4 ninja openldap openssh patchutils perl pkg-config.pkg-config python3 scons
            #             serf sqlite subversion sysctl.provider texinfo unzip which
            #             ]);

            #             assert prevStage.darwin.cctools == prevStage.darwin.cctools-llvm;

            #             let
            #             doSign = localSystem.isAarch64;

            #             cc = prevStage.llvmPackages.clang;
            #             in
            #             {
            #             inherit config overlays;
            #             stdenv = import ../generic {
            #             name = "stdenv-darwin";

            #             buildPlatform = localSystem;
            #             hostPlatform = localSystem;
            #             targetPlatform = localSystem;

            #             inherit config;

            #             preHook = ''
            #                 ${commonPreHook}
            #                 stripDebugFlags="-S" # llvm-strip does not support "-p" for Mach-O
            #                 export PATH_LOCALE=${prevStage.darwin.locale}/share/locale
            #             '';

            #             initialPath = ((import ../generic/common-path.nix) { pkgs = prevStage; });

            #             extraNativeBuildInputs = lib.optionals localSystem.isAarch64 [
            #                 prevStage.updateAutotoolsGnuConfigScriptsHook
            #             ] ++ [ prevStage.darwin.apple_sdk.sdkRoot ];

            #             extraBuildInputs = [ prevStage.darwin.CF ];

            #             inherit cc;

            #             shell = cc.shell;

            #             inherit (prevStage.stdenv) fetchurlBoot;

            #             extraAttrs = {
            #                 inherit bootstrapTools;
            #                 libc = prevStage.darwin.Libsystem;
            #                 shellPackage = prevStage.bash;
            #             } // lib.optionalAttrs useAppleSDKLibs {
            #                 # This objc4 will be propagated to all builds using the final stdenv,
            #                 # and we shouldn't mix different builds, because they would be
            #                 # conflicting LLVM modules. Export it here so we can grab it later.
            #                 inherit (prevStage.darwin) objc4;
            #             };

            #             disallowedRequisites = [ bootstrapTools.out ];

            #             allowedRequisites = (with prevStage; [
            #                 bash
            #                 binutils.bintools
            #                 binutils.bintools.lib
            #                 bzip2.bin
            #                 bzip2.out
            #                 cc.expand-response-params
            #                 coreutils
            #                 darwin.binutils
            #                 darwin.binutils.bintools
            #                 diffutils
            #                 ed
            #                 file
            #                 findutils
            #                 gawk
            #                 gettext
            #                 gmp.out
            #                 gnugrep
            #                 gnugrep.pcre2.out
            #                 gnumake
            #                 gnused
            #                 gnutar
            #                 gzip
            #                 icu.out
            #                 libffi.out
            #                 libiconv
            #                 libunistring.out
            #                 libxml2.out
            #                 ncurses.dev
            #                 ncurses.man
            #                 ncurses.out
            #                 openbsm
            #                 openpam
            #                 patch
            #                 xz.bin
            #                 xz.out
            #                 zlib.dev
            #                 zlib.out
            #             ]
            #             ++ lib.optionals doSign [ openssl.out ])
            #             ++ lib.optionals localSystem.isAarch64 [
            #                 prevStage.updateAutotoolsGnuConfigScriptsHook
            #                 prevStage.gnu-config
            #             ]
            #             ++ (with prevStage.llvmPackages; [
            #                 bintools-unwrapped
            #                 clang-unwrapped
            #                 clang-unwrapped.lib
            #                 compiler-rt
            #                 compiler-rt.dev
            #                 libcxx
            #                 libcxx.dev
            #                 lld
            #                 llvm
            #                 llvm.lib
            #             ])
            #             ++ (with prevStage.darwin; [
            #                 CF
            #                 Libsystem
            #                 cctools-llvm
            #                 cctools-port
            #                 dyld
            #                 libtapi
            #                 locale
            #                 apple_sdk.sdkRoot
            #             ]
            #             ++ lib.optional useAppleSDKLibs [ objc4 ]
            #             ++ lib.optionals doSign [ postLinkSignHook sigtool signingUtils ]);

            #             __stdenvImpureHostDeps = commonImpureHostDeps;
            #             __extraImpureHostDeps = commonImpureHostDeps;

            #             overrides = self: super: {
            #                 inherit (prevStage)
            #                 bash binutils brotli bzip2 coreutils cpio diffutils ed file findutils gawk
            #                 gettext gmp gnugrep gnumake gnused gnutar gzip icu libffi libiconv libidn2 libssh2
            #                 libunistring libxml2 libyaml ncurses nghttp2 openbsm openpam openssl patch pbzx
            #                 pcre python3Minimal xar xz zlib zstd;

            #                 darwin = super.darwin.overrideScope (_: superDarwin: {
            #                 inherit (prevStage.darwin)
            #                     CF ICU Libsystem darwin-stubs dyld locale libobjc libtapi rewrite-tbd xnu;

            #                 apple_sdk = superDarwin.apple_sdk // {
            #                     inherit (prevStage.darwin.apple_sdk) sdkRoot;
            #                 };
            #                 } // lib.optionalAttrs (super.stdenv.targetPlatform == localSystem) {
            #                 inherit (prevStage.darwin) binutils binutils-unwrapped cctools-llvm cctools-port;
            #                 });
            #             } // lib.optionalAttrs (super.stdenv.targetPlatform == localSystem) {
            #                 inherit (prevStage.llvmPackages) clang llvm;

            #                 # Need to get rid of these when cross-compiling.
            #                 llvmPackages = super.llvmPackages // (
            #                 let
            #                     tools = super.llvmPackages.tools.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) clang clang-unwrapped libclang libllvm llvm;
            #                     });
            #                     libraries = super.llvmPackages.libraries.extend (_: _: {
            #                     inherit (prevStage.llvmPackages) compiler-rt libcxx;
            #                     });
            #                 in
            #                 { inherit tools libraries; } // tools // libraries
            #                 );

            #                 inherit (prevStage) binutils binutils-unwrapped;
            #             };
            #             };
            #         })

            #         # This "no-op" stage is just a place to put the assertions about stage6.
            #         (prevStage:
            #             # previous final stage stdenv:
            #             assert isBuiltByNixpkgsCompiler prevStage.darwin.sigtool;
            #             assert isBuiltByNixpkgsCompiler prevStage.darwin.binutils-unwrapped;
            #             assert isBuiltByNixpkgsCompiler prevStage.darwin.print-reexports;
            #             assert isBuiltByNixpkgsCompiler prevStage.darwin.rewrite-tbd;
            #             assert isBuiltByNixpkgsCompiler prevStage.darwin.cctools;

            #             assert            isFromNixpkgs prevStage.darwin.CF;
            #             assert            isFromNixpkgs prevStage.darwin.Libsystem;

            #             assert isBuiltByNixpkgsCompiler prevStage.llvmPackages.clang-unwrapped;
            #             assert isBuiltByNixpkgsCompiler prevStage.llvmPackages.libllvm;
            #             assert isBuiltByNixpkgsCompiler prevStage.llvmPackages.libcxx;
            #             assert isBuiltByNixpkgsCompiler prevStage.llvmPackages.compiler-rt;
            #             { inherit (prevStage) config overlays stdenv; })
            #         ]