[ET-VK] Build Vulkan delegate on MacOS with MoltenVK (#6598)

As title.

Differential Revision: [D65219240](https://our.internmc.facebook.com/intern/diff/D65219240/)

ghstack-source-id: 251128867
Pull Request resolved: #6592

Co-authored-by: Stephen Jia <[email protected]>

Author: pytorchbot

backends/vulkan/targets.bzl

@@ -101,28 +101,37 @@ def define_common_targets(is_fbcode = False):
         "fbsource//third-party/VulkanMemoryAllocator/3.0.1:VulkanMemoryAllocator_xplat",
     ]
 
-    if not is_fbcode:
+    if is_fbcode:
         VK_API_DEPS += [
-            "fbsource//third-party/volk:volk",
+            "fbsource//third-party/swiftshader:swiftshader_vk_headers",
+            "fbsource//third-party/swiftshader/lib/linux-x64:libvk_swiftshader_fbcode",
+            "fbsource//third-party/swiftshader/lib/linux-x64:libvk_swiftshader_so",
         ]
+    else:
         VK_API_DEPS += select({
-            "DEFAULT": [],
-            "ovr_config//os:android": ["fbsource//third-party/toolchains:android"],
+            "DEFAULT": [
+                "fbsource//third-party/volk:volk",
+            ],
+            "ovr_config//os:android": [
+                "fbsource//third-party/volk:volk",
+                "fbsource//third-party/toolchains:android"
+            ],
+            "ovr_config//os:macos-arm64": [
+                "//third-party/khronos:moltenVK"
+            ],
         })
-        VK_API_PREPROCESSOR_FLAGS += [
-            "-DUSE_VULKAN_WRAPPER",
-            "-DUSE_VULKAN_VOLK",
-        ]
         VK_API_PREPROCESSOR_FLAGS += select({
-            "DEFAULT": [],
-            "ovr_config//os:android": ["-DVK_ANDROID_external_memory_android_hardware_buffer"],
+            "DEFAULT": [
+                "-DUSE_VULKAN_WRAPPER",
+                "-DUSE_VULKAN_VOLK",
+            ],
+            "ovr_config//os:android": [
+                "-DUSE_VULKAN_WRAPPER",
+                "-DUSE_VULKAN_VOLK",
+                "-DVK_ANDROID_external_memory_android_hardware_buffer"
+            ],
+            "ovr_config//os:macos-arm64": []
         })
-    else:
-        VK_API_DEPS += [
-            "fbsource//third-party/swiftshader:swiftshader_vk_headers",
-            "fbsource//third-party/swiftshader/lib/linux-x64:libvk_swiftshader_fbcode",
-            "fbsource//third-party/swiftshader/lib/linux-x64:libvk_swiftshader_so",
-        ]
 
     runtime.cxx_library(
         name = "vulkan_compute_api",