glibcLocales: fix tarball on Darwin

[Mathnerd314]

https://hydra.nixos.org/build/26376016/nixlog/1/raw

I'm not sure why it worked before.

[vcunat]

This might not be a good idea. I suspect darwin people rely on similar attributes to be null, so they can be passed to buildInputs regardless of platform and really get in there only on linux. There were also those *OrEmpty and *OrNull idioms; I'm not sure what's best.

[vcunat]

For now, I fixed the tarball without changing glibcLocales semantics.

I really do dislike the fact that even if one specifies meta.platforms = platforms.linux, the tarball does try to evaluate the package build phases on darwin. IMO that should be changed.

[domenkozar]

Closing this as it's solved, do open an issue if you want to discuss what's the best method for such evaluation errors.

[Mathnerd314]

I think #6561 can be that issue, as it is strongly related.