[PATCH v2] 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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On Thu, Apr 21 2022, Phillip Wood wrote:

Urgh, sorry. I don't know how I got that turned around, but this version works, and the (currently ongoing) CI run shows that the linux-gcc job selects gcc-8 correctly, instead of gcc:

    https://github.com/avar/git/runs/6116735686?check_suite_focus=true#step:3:22

The osx-gcc job will be likewise fixed, but it's failing in that run due to the unrelated perforce installation issue affecting all OSX jobs (fix here: https://lore.kernel.org/git/cover-0.2-00000000000-20220421T124225Z-avarab@gmail.com/).

Range-diff against v1:
1:  d89ad4d5b7c ! 1:  92acf9420a9 CI: select CC based on CC_PACKAGE (again)
    @@ ci/lib.sh: then
      	CI_REPO_SLUG="$GITHUB_REPOSITORY"
      	CI_JOB_ID="$GITHUB_RUN_ID"
     -	CC="${CC:-gcc}"
    -+	CC="${CC:-${CC_PACKAGE:-gcc}}"
    ++	CC="${CC_PACKAGE:-${CC:-gcc}}"
      	DONT_SKIP_TAGS=t
      
      	cache_dir="$HOME/none"

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