Provide a way to exclude packages from flake check

[kjeremy]

Is your feature request related to a problem? Please describe.
NixOS/nixpkgs#338231 makes nix flake check consistently OOM for flakes that make heavy use of python and cross compilation.

Describe the solution you'd like
I would like to be able to exclude cross compiled packages (or others?) from nix flake check possibly through some filter function in the flake.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

Priorities

Add 👍 to issues you find important.

[Mic92]

If you have a smaller packages, you can also mitigate the issue a bit using https://github.com/Mic92/nix-fast-build