wine-packages: fix Hydra build failures on Darwin

Disable Vulkan and VKD3D by default on Darwin while MoltenVK is forced
to build using Xcode instead of the SDK in nixpkgs. They can be
overriden if the user needs either of those.

pkgs/top-level/wine-packages.nix

@@ -12,7 +12,8 @@ rec {
     fontconfigSupport = stdenv.isLinux;
     alsaSupport = stdenv.isLinux;
     openglSupport = true;
-    vulkanSupport = true;
+    # Works on Darwin but disabled by default to prevent Hydra build failures due to MoltenVK.
+    vulkanSupport = stdenv.isLinux;
     tlsSupport = true;
     cupsSupport = true;
     dbusSupport = stdenv.isLinux;
@@ -40,7 +41,8 @@ rec {
     gphoto2Support = true;
     krb5Support = true;
     ldapSupport = true;
-    vkd3dSupport = true;
+    # Works on Darwin but disabled by default to prevent Hydra build failures due to MoltenVK.
+    vkd3dSupport = stdenv.isLinux;
     embedInstallers = true;
   };