stage.nix: revert deletion of gcc.abi="elfv2" from 82ff1f5

Commit 82ff1f5db12f862e226e84254e54a10879f1629b in #182807 removed two lines
from stage.nix which were responsible for making sure the `gcc` for `pkgsStatic`
on powerpc64 was built with the `--with-abi=elfv2` flag.

Unfortunately this causes build failures for `pkgsCross.ppc64.pkgsStatic`, as
reported here:

  https://github.com/NixOS/nixpkgs/pull/182807#issuecomment-1247268226

This commit reverts the deletion.

Unfortunately ugly kludges like this are necessary because nixpkgs'
`lib/systems/` doesn't understand the difference between a libc and an abi.  So
we have no clean way to tell nixpkgs "musl on big-endian powerpc64 always uses
the ELFv2 ABI" -- it thinks that musl is an ABI.  Until that gets fixed there is
no better way to add the flag.

0 files changed, 0 insertions, 0 deletions