zink: Fix building on macOS

This commit fixes building of zink on macOS. It is not supposed to guarantee that zink will work flawlessly on macOS.

It fixes it with a new file zink_MVK_VERSION.h that correctly includes MoltenVK/vk_mvk_moltenvk.h (it doesn't include the vulkan headers it needs itself)

To build on macOS, you will probably need to run: brew install bison llvm cmake libxext xquartz ninja xorgproto meson And you also need to setup meson with something like: -Dmoltenvk-dir=/Users//VulkanSDK//MoltenVK -Dc_std=c11

Please help me through this MR, I haven't contributed to mesa or used gitlab before.

This fixes the build issues in #5736 (closed).