refactor: better macOS exclusive options

machines/common/darwin/default.nix

@@ -1,4 +1,5 @@
 {lib, ...}: {
+  imports = [./options.nix];
   # manipulate the global /etc/zshenv for PATH, etc.
   programs.zsh.enable = true;
 

machines/common/darwin/options.nix

@@ -0,0 +1,8 @@
+{lib, ...}: let
+  inherit (lib) mkOption types;
+in {
+  options.location = {
+    latitude = mkOption {type = types.nullOr types.float;};
+    longitude = mkOption {type = types.nullOr types.float;};
+  };
+}

machines/lib.nix

@@ -74,14 +74,6 @@
           ./${host}
           home-manager.${module}.home-manager
         ]
-        ++ pkgs.lib.optionals pkgs.stdenv.isDarwin [
-          {
-            options.location = {
-              latitude = mkOption {type = types.nullOr types.float;};
-              longitude = mkOption {type = types.nullOr types.float;};
-            };
-          }
-        ]
         ++ [(hmCommonConfig {inherit username;})]
         ++ extraModules;
       specialArgs = {inherit inputs;};