This requires knock-on upgrades for glslang and spirv-tools.
I have also made the validation layers easier to use:
- library files identified by layer definitions now use absolute paths
- the layer definition path is prepended to XDG_DATA_DIRS
Previously, one would have to modify LD_LIBRARY_PATH or install the
derivation in a known location for vulkan-loader to find relevant
files. These changes make using validation layers in a nix-shell work automatically.
Use XDG_DATA_DIRS environment variable rather than VK_LAYER_PATH
