llama.cpp Vulkan backend requires SPIR-V headers package now

If you don't install SPIR-V headers it will no longer compile, keep that in mind: https://github.com/ggml-org/llama.cpp/pull/21572/changes#diff-43453f510556d352276e897e137cb103b3bbca24acb6cba33208d4887b2e3c77R497