Tidy up legacyPackages instantiation

flake.nix

@@ -180,22 +180,19 @@
 
         });
 
-      legacyPackages =
-        # The nixpkgs.legacyPackages set after overlaying.
-        let f = import nixpkgs;
-        in forAllSystems ({ system, localSystem, crossSystem }:
-          if localSystem == crossSystem then
-            nixpkgs.legacyPackages.${system}.appendOverlays overlays
-          else
-            f {
-              inherit localSystem;
-              crossSystem = {
-                system = crossSystem;
-                useLLVM = true;
-              };
-              config.allowUnsupportedSystem = true;
-              inherit overlays;
-            });
+      legacyPackages = forAllSystems ({ system, localSystem, crossSystem }:
+        if builtins.hasAttr system nixpkgs.legacyPackages then
+          nixpkgs.legacyPackages.${system}.appendOverlays overlays
+        else
+          import nixpkgs {
+            inherit localSystem;
+            crossSystem = {
+              system = crossSystem;
+              useLLVM = true;
+            };
+            config.allowUnsupportedSystem = true;
+            inherit overlays;
+          });
 
       packages =
         # Genode native packages, not packages in the traditional

nixos-modules/default.nix

@@ -13,7 +13,7 @@
       ./qemu-vm.nix
       ./services
     ];
-    nixpkgs = {
+    nixpkgs = rec {
       localSystem.system = "x86_64-linux";
       crossSystem.system = "x86_64-genode";
       system = localSystem.system + "-" + crossSystem.system;