icd: Add build support for iOS and Metal surfaces

The CMakelists.txt only enabled the MACOS_MVK surface extension, so this
makes MockICD more flexible for users.

Author: charles-lunarg

icd/CMakeLists.txt

@@ -30,7 +30,12 @@ option(BUILD_MOCK_ANDROID_SUPPORT "Build with Android Platform headers" OFF)
 if(WIN32)
     add_definitions(-DVK_USE_PLATFORM_WIN32_KHR -DVK_USE_PLATFORM_WIN32_KHX -DWIN32_LEAN_AND_MEAN)
 elseif(APPLE)
-    add_definitions(-DVK_USE_PLATFORM_MACOS_MVK)
+    add_definitions(-DVK_USE_PLATFORM_METAL_EXT)
+    if (IOS)
+        add_definitions(-DVK_USE_PLATFORM_IOS_MVK)
+    else()
+        add_definitions(-DVK_USE_PLATFORM_MACOS_MVK)
+    endif()
 elseif(BUILD_MOCK_ANDROID_SUPPORT)
     add_definitions(-DVK_USE_PLATFORM_ANDROID_KHR)
 elseif(CMAKE_SYSTEM_NAME MATCHES "Linux|BSD|GNU")