[Important] Adds advanced flake.nix for $ nix build github:KhronosGroup/OpenCL-ICD-Loader and more

[izelnakri]

Hi there,

Currently I'm working on standardizing, further specifying and simplifying the build, test and release of all the GPU based software for nix: which should eventually allow all standard bodies and hardware/software vendors to further standardize their build workflows.

We already have khronos-ocl-icd-loader on nixpkgs here: https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/kh/khronos-ocl-icd-loader/package.nix

This flake.nix serves as an additional release channel for a direct specific github branch on any machine that has nix via:

$ nix build github:KhronosGroup/OpenCL-ICD-Loader # or:
$ nix build github:KhronosGroup/OpenCL-ICD-Loader/ad770a1b64c6b8d5f2ed4e153f22e4f45939f27f # or:
$ nix build github:KhronosGroup/OpenCL-ICD-Loader/v2025.07.22

Also serves as a further documentation as code for all the important build targets.

It also standardizes the builds under a single command:

$ nix build ".#" # Runs the unit tests as well, nix testing convention, there is doCheck = true
$ tree ./result
result
├── bin
│   └── cllayerinfo
├── lib
│   ├── libOpenCL.so -> libOpenCL.so.1
│   ├── libOpenCL.so.1 -> libOpenCL.so.1.0.0
│   ├── libOpenCL.so.1.0.0
│   └── pkgconfig
│       └── OpenCL.pc
└── share
    └── cmake
        └── OpenCLICDLoader
            ├── OpenCLICDLoaderConfig.cmake
            ├── OpenCLICDLoaderConfigVersion.cmake
            ├── OpenCLICDLoaderTargets.cmake
            └── OpenCLICDLoaderTargets-release.cmake

7 directories, 9 files

A contributor can have standardized development environment via:

$ nix develop # Could also automatically if the developer has `direnv` installed & configured
# With the current flake.nix, then developer can see the output:
$ pkg-config --list-all --cflags
OpenCL-Headers OpenCL-Headers - Khronos OpenCL Headers
OpenCL         OpenCL - Khronos OpenCL ICD Loader

Lastly, in the future, if there is enough interest, this could enhance the existing CI workflow(with additional PRs) via:

$ nix flake check --all-systems # Runs all the checks(unit tests, pkg-config checks etc) on all CPU architectures

On a corollary note, I suggest all software developers to install and use nix for all its benefits. I think there is enough documentation online, however I currently find the documentation lacking for conventions around testing. So I documented it here for the ones interested: https://gist.github.com/izelnakri/06d7286fe9ab5f15acee9cbeace1c1b1

[CLAassistant]

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