Support Asahi / apple silicon

[TheButlah]

The mesa drivers that the ICDs come from don't seem to include asahi's ICD. For context, this is asahi's ICD:

❯ cat asahi_icd.aarch64.json   
{
    "ICD": {
        "api_version": "1.4.311",
        "library_path": "/usr/lib64/libvulkan_asahi.so"
    },
    "file_format_version": "1.0.0"
}

[neobrain]

This is fixed by using a more up-to-date nixpkgs version than the one pinned in flake.lock. Presumably the old mesa derivation didn't include Asahi drivers by default.

Running nix flake update && nix profile install .#nixVulkanIntel within a nixGL source checkout makes it work.