Fix broken Vulkan Cmake

[netrunnereve]

With this Vulkan Cmake should now compile properly. The Makefile works fine, it's only Cmake that errors out.

[sorasoras]

I think this break my compile on windows.
@netrunnereve

  Generating Code...
  ggml-vulkan.cpp
C:\Users\Sora\Desktop\git\llama.cpp\ggml-vulkan.cpp(7,10): fatal  error C1083: Cannot open include file: 'vulkan/vulkan
.hpp': No such file or directory [C:\Users\Sora\Desktop\git\llama.cpp\vulkan\ggml.vcxproj]