Cross-compile s390x packages from x86_64-linux

flake.nix

@@ -22,34 +22,78 @@
         "s390x-linux"
       ];
     in
-    flake-utils.lib.eachSystem supportedSystems (
-      system:
-      let
-        pkgs = import nixpkgs { inherit system; };
-      in
-      {
-        packages = rec {
-          hello-world = pkgs.callPackage ./packages/hello-world.nix { };
-          xonsh = pkgs.callPackage ./packages/xonsh.nix { };
-          default = hello-world;
-        };
+    let
+      # Systems that have native builders
+      buildSystems = [
+        "x86_64-linux"
+        "aarch64-linux"
+      ];
 
-        overlays.default = final: prev: {
-          hello-world = final.callPackage ./packages/hello-world.nix { };
-          xonsh = final.callPackage ./packages/xonsh.nix { };
-        };
+      # Cross-compilation targets from x86_64-linux
+      crossTargets = {
+        "s390x-linux" = "s390x-linux";
+      };
 
-        devShells.default = pkgs.mkShell {
-          name = "oleks-hub-shell";
-          buildInputs = [ self.packages.${system}.default ];
-          nativeBuildInputs = with pkgs; [
-            nix
-            fmt
-          ];
-          shellHook = ''
-            echo "Welcome to the oleks Flake hub development shell."
-          '';
-        };
-      }
-    );
+      mkPackages = pkgs: {
+        hello-world = pkgs.callPackage ./packages/hello-world.nix { };
+        xonsh = pkgs.callPackage ./packages/xonsh.nix { };
+      };
+
+      # Native builds
+      native = flake-utils.lib.eachSystem buildSystems (
+        system:
+        let
+          pkgs = import nixpkgs { inherit system; };
+          packages = mkPackages pkgs;
+        in
+        {
+          packages = packages // {
+            default = packages.hello-world;
+          };
+
+          overlays.default = final: prev: mkPackages final;
+
+          devShells.default = pkgs.mkShell {
+            name = "oleks-hub-shell";
+            buildInputs = [ self.packages.${system}.default ];
+            nativeBuildInputs = with pkgs; [
+              nix
+              fmt
+            ];
+            shellHook = ''
+              echo "Welcome to the oleks Flake hub development shell."
+            '';
+          };
+        }
+      );
+
+      # Cross-compiled builds (built from x86_64-linux)
+      cross = builtins.listToAttrs (
+        builtins.map (
+          target:
+          let
+            pkgs = import nixpkgs {
+              system = "x86_64-linux";
+              crossSystem.config = nixpkgs.lib.systems.examples.${
+                {
+                  "s390x-linux" = "s390x";
+                }
+                .${target}
+              }.config;
+            };
+            packages = mkPackages pkgs;
+          in
+          {
+            name = target;
+            value = packages // {
+              default = packages.hello-world;
+            };
+          }
+        ) (builtins.attrNames crossTargets)
+      );
+    in
+    native
+    // {
+      packages = (native.packages or { }) // cross;
+    };
 }