set gcc.arch, extra-platforms, system-features

modules/nixos/common/builder.nix

@@ -19,6 +19,30 @@
       script = builtins.readFile "${inputs.self}/modules/shared/free-space.bash";
     };
 
+    nixpkgs.hostPlatform = {
+      inherit (pkgs.hostPlatform) system;
+    };
+
+    nix.settings.extra-platforms = lib.mkIf (config.nixpkgs.hostPlatform.system == "x86_64-linux") [
+      (lib.mkIf (config.boot.binfmt.emulatedSystems == [ ]) "i686-linux")
+      "x86_64-v1-linux"
+      "x86_64-v2-linux"
+      "x86_64-v3-linux"
+      (lib.mkIf (builtins.elem "gccarch-x86-64-v4" config.nix.settings.system-features) "x86_64-v4-linux")
+    ];
+
+    nix.settings.system-features =
+      [
+        "benchmark"
+        "big-parallel"
+        "kvm"
+        "nixos-test"
+        "gccarch-${config.nixpkgs.hostPlatform.gcc.arch}"
+      ]
+      ++ map (x: "gccarch-${x}") (
+        lib.systems.architectures.inferiors.${config.nixpkgs.hostPlatform.gcc.arch} or [ ]
+      );
+
     # Bump the open files limit so that non-root users can run NixOS VM tests
     security.pam.loginLimits = [
       {