This will allow buliding bootstrap tools for platforms with
non-default libcs, like *-unknown-linux-musl.
This gets rid of limitedSupportSystems/systemsWithAnySupport. There
was no need to use systemsWithAnySupport for supportDarwin, because it
was always equivalent to supportedSystems for that purpose, and the
only other way it was used was for determining which platforms to
build the bootstrap tools for, so we might as well use a more explicit
parameter for that, and then we can change how it works without
affecting the rest of the Hydra jobs.
Not affecting the rest of the Hydra jobs is important, because if we
changed all jobs to use config triples, we'd end up renaming every
Hydra job. That might still be worth thinking about at some point,
but it's unnecessary at this point (and would be a lot of work).
I've checked by running
nix-eval-jobs --force-recurse pkgs/top-level/release.nix
that the actual bootstrap tools derivations are unaffected by this
change, and that the only other jobs that change are ones that depend
on the hash of all of Nixpkgs. Of the other jobset entrypoints that
end up importing pkgs/top-level/release.nix, none used the
limitedSupportedSystems parameter, so they should all be unaffected as
well.
