Vulkan shader compiler accesses the cache folder via multiple threads.
GHOST part isn't thread safe and can return and overwrite the returned
cache path. This resulted into crashes when performing background
rendering and failing test cases, loading of incorrect shaders etc.
This PR fixes this to cache the cache folder location in the
VKShaderCompiler, which is loaded via the main thread when the vulkan
backend is initialized.
Pull Request: https://projects.blender.org/blender/blender/pulls/133535
e2dddea124