core/pkgs/by-name/pk/pkg-config/packages.nix

{ ... }:
res: pkgs: super:

with pkgs; {
  pkg-config-unwrapped = callPackage ./. { };

  pkg-configUpstream = lowPrio (
    pkg-config.override (old: {
      pkg-config = old.pkg-config.override { vanilla = true; };
    })
  );

  pkg-config = callPackage (path + "/pkgs/build-support/pkg-config-wrapper") {
    pkg-config = pkg-config-unwrapped;
  };
}