[PATCH] CI: select CC based on CC_PACKAGE (again)

Fix a regression in 707d2f2fe86 (CI: use "$runs_on_pool", not "$jobname" to select packages & config, 2021-11-23).

In that commit I changed CC=gcc from CC=gcc-9, but on OSX the "gcc" in $PATH points to clang, we need to use gcc-9 instead. Likewise for the linux-gcc job CC=gcc-8 was changed to the implicit CC=gcc, which would select GCC 9.4.0 instead of GCC 8.4.0.

Furthermore in 25715419bf4 (CI: don't run "make test" twice in one job, 2021-11-23) when the "linux-TEST-vars" job was split off from "linux-gcc" the "cc_package: gcc-8" line was copied along with it.

That wasn't a bug per-se, as that "make test" would have run under GCC 8 before the split into two jobs, but the point of selecting different compiler for these jobs is to get better coverage, and to narrow down any issues with a given compiler to the job that runs it. Since the "linux-TEST-vars" job is already special in other ways (in running with various GIT_TEST_* variables), and we've got the "linux-gcc" job covering gcc-8 let's have it used the default system compiler instead.

Reported-by: Carlo Arenas <carenas@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
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Range-diff:
1:  94abb826627 < -:  ----------- CI: have osx-gcc use gcc, not clang
-:  ----------- > 1:  d89ad4d5b7c CI: select CC based on CC_PACKAGE (again)

The range-diff is against a relevant patch in v4 of a larger CI series of mine[1]. This fix is independent of that, and on top of master. See [2] for the original fix and discussion.

As noted in the updated commit message not only the OSX jobs were affected, but also the linux-gcc job. This fixes both, along with a small fix to the related linux-TEST-vars recipe.

1. https://lore.kernel.org/git/cover-v4-00.31-00000000000-20220418T132809Z-avarab@gmail.com/
2. https://lore.kernel.org/git/patch-v4-30.31-94abb826627-20220418T132809Z-avarab@gmail.com/

 .github/workflows/main.yml | 1 -
 ci/lib.sh                  | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)