refactor to fix dependency on 'osConfig' arg

modules/global/options.nix

@@ -49,6 +49,11 @@
           type = lib.types.str;
           default = "";
         };
+
+        isStandalone = lib.mkOption {
+          type = lib.types.bool;
+          default = false;
+        };
       };
       
       features.applications.extraPackages = lib.mkOption {