cudaPackages: proper FindCUDAToolkit.cmake support

[SomeoneSerge]

• https://gitlab.kitware.com/cmake/cmake/-/issues/24663
• Remove symlinkJoin from packages that support CUDAToolkit
• Proof of concept:
  • We need setup-hooks that would populate CUDAToolkit_ROOT and CUDAToolkit_INCLUDE_DIR search paths: https://github.com/SomeoneSerge/nix-findcudatoolkit-cmake/blob/8cc915863e16433eee4ed3852c395734201f840f/use-cudatoolkit-root.nix#L19-L22
  • And we need to navigate our cuda_nvcc so that it knows where cudart lives (for cmake compiler checks that are performed before FindCUDAToolkit.cmake): https://github.com/SomeoneSerge/nix-findcudatoolkit-cmake/blob/8cc915863e16433eee4ed3852c395734201f840f/use-cudatoolkit-root.nix#L48

[SomeoneSerge]

Note that currently our pkg-config is broken too: #224119

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/cuda-team-roadmap-and-call-for-sponsors/29495/1

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/cuda-team-roadmap-update-2023-08-29/32379/1