[Nix-dev] Stablilizing stdenv-updates

[Peter Simons]

Hi Ludovic,

I completely agree that we should not waste a precious resource like
Hydra for hundreds of unnecessary builds. stdenv-updates doesn't need to
build all of "release.nix" just to be useful for testing, and we
shouldn't enable all those builds right now.

It is sufficient to build CUPS itself to allow us to work on that
update. Once both CUPS and glibc are up-to-date, it should be possible
to build a bigger package set.

Take care,
Peter