emit CMake message about MoltenVK Vulkan compat

cmake/check_vulkan_version.cmake

@@ -131,7 +131,11 @@ function(check_vulkan_version)
     endforeach()
 
     if("${VALID_GPU}" STREQUAL "")
-        message(FATAL_ERROR "None of your GPUs supports Vulkan Header ${VULKAN_HEADER_VERSION}. Please try updating your driver, or downgrade your Vulkan headers. If you know what you are doing, you can disable the Vulkan version check by setting 'KOMPUTE_OPT_DISABLE_VULKAN_VERSION_CHECK' to 'ON' (-DKOMPUTE_OPT_DISABLE_VULKAN_VERSION_CHECK=ON).")
+        if (APPLE)
+            message(FATAL_ERROR "You are on an Apple platform, likely using the MoltenVK Vulkan driver. MoltenVK's device driver doesn't fully implement Vulkan 1.3 yet, but 1.3 Vulkan instances are supported. Please see https://github.com/KhronosGroup/MoltenVK/issues/1930 for MoltenVK's Vulkan 1.3 support status. In the mean time, please set 'KOMPUTE_OPT_DISABLE_VULKAN_VERSION_CHECK' to 'ON' (-DKOMPUTE_OPT_DISABLE_VULKAN_VERSION_CHECK=ON) and Kompute should work.")
+        else()
+            message(FATAL_ERROR "None of your GPUs supports Vulkan Header ${VULKAN_HEADER_VERSION}. Please try updating your driver, or downgrade your Vulkan headers. If you know what you are doing, you can disable the Vulkan version check by setting 'KOMPUTE_OPT_DISABLE_VULKAN_VERSION_CHECK' to 'ON' (-DKOMPUTE_OPT_DISABLE_VULKAN_VERSION_CHECK=ON).")
+      endif()
     else()
         message("Valid GPU (${VALID_GPU}) for Vulkan header version ${VULKAN_HEADER_VERSION} found. ${VALID_GPU} supports up to Vulkan ${VALID_VULKAN_VERSION}.")
     endif()