feat: dynamic cross packages generation

potluck/src/packages/default.nix

@@ -8,9 +8,32 @@
 
   generic = config.packages.generic;
 
-  targeted = {
+  getPackages = system:
-    i686-linux = generic;
+    builtins.mapAttrs
+    (
+      namespace: packages:
+        lib.attrs.filter
+        (name: package: builtins.elem system package.meta.platforms)
+        packages
+    );
+
+  targeted' = {
+    i686-linux =
+      getPackages "i686-linux" generic
+      // {
+        cross = {
+          x86_64-linux = getPackages "x86_64-linux" generic;
         };
+      };
+  };
+
+  targeted = lib.attrs.generate lib'.systems.doubles.all (system:
+    getPackages system generic
+    // {
+      cross = lib.attrs.generate doubles (
+        host: getPackages host generic
+      );
+    });
 in {
   includes = [
     # ./aux/foundation.nix
@@ -34,16 +57,19 @@ in {
       generic = {
         example = {
           x = {
+            meta.platforms = ["i686-linux" "x86_64-linux"];
             version = "1.0.0";
+
             builder.build = package:
               derivation {
                 name = package.name;
                 builder = "/bin/sh";
                 system = package.platform.build;
               };
+
             phases = {
-              build = ''
+              build = package: ''
-                make
+                make --build ${package.platform.build} --host ${package.platform.host}
               '';
 
               install = lib.dag.entry.after ["build"] ''