Merge pull request #250489 from amjoseph-nixpkgs/pr/gcc/deduplicate-s…

…taging

gcc: deduplicate version expressions

The last merge of `staging` into `master` caused a really nasty merge conflict here.

Since this is strictly cleanup (no change after eval), in order to prevent that from happening again I am merging this to both `master` and `staging`.  It's much easier to rebase other patches past this one than it is to rebase this one past other patches.