[PATCH v4 26/31] CI: set CC in MAKEFLAGS directly, don't add it to the environment

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Rather than pass a "$CC" in the environment to be picked up in
ci/lib.sh let's instead have ci/lib.sh itself add it directly to
MAKEFLAGS. For "$CC_PACKAGE" its setting and use can stay within
ci/install-dependencies.sh.

Setting CC=gcc by default made for confusing trace output, and since a
preceding change to carry it and others over across "steps" in the
GitHub CI it's been even more misleading.  E.g. the "win+VS build" job
confusingly has CC=gcc set, even though it builds with MSVC.

Let's instead rely on the Makefile default of CC=cc, and only override
it for those jobs where it's needed. This does mean that we'll need to
set it for the "pedantic" job, which previously relied on the default
CC=gcc in case "clang" become the default on that platform.

This partially reverts my 707d2f2fe86 (CI: use "$runs_on_pool", not
"$jobname" to select packages & config, 2021-11-23), i.e. we're now
aiming to only set those variables specific jobs need.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 .github/workflows/main.yml | 13 -------------
 ci/install-dependencies.sh | 10 ++++++++++
 ci/lib.sh                  | 23 ++++++++++++++++++++---
 3 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 0787cadc76b..6d25ec4ae3b 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -238,37 +238,24 @@ jobs:
       matrix:
         vector:
           - jobname: linux-clang
-            cc: clang
             pool: ubuntu-latest
           - jobname: linux-sha256
-            cc: clang
             os: ubuntu
             pool: ubuntu-latest
           - jobname: linux-gcc
-            cc: gcc
-            cc_package: gcc-8
             pool: ubuntu-latest
           - jobname: linux-TEST-vars
-            cc: gcc
             os: ubuntu
-            cc_package: gcc-8
             pool: ubuntu-latest
           - jobname: osx-clang
-            cc: clang
             pool: macos-latest
           - jobname: osx-gcc
-            cc: gcc
-            cc_package: gcc-9
             pool: macos-latest
           - jobname: linux-gcc-default
-            cc: gcc
             pool: ubuntu-latest
           - jobname: linux-leaks
-            cc: gcc
             pool: ubuntu-latest
     env:
-      CC: ${{matrix.vector.cc}}
-      CC_PACKAGE: ${{matrix.vector.cc_package}}
       jobname: ${{matrix.vector.jobname}}
       runs_on_pool: ${{matrix.vector.pool}}
     runs-on: ${{matrix.vector.pool}}
diff --git a/ci/install-dependencies.sh b/ci/install-dependencies.sh
index 52f2180d5b4..1d05f43d19e 100755
--- a/ci/install-dependencies.sh
+++ b/ci/install-dependencies.sh
@@ -9,6 +9,16 @@ UBUNTU_COMMON_PKGS="make libssl-dev libcurl4-openssl-dev libexpat-dev
  tcl tk gettext zlib1g-dev perl-modules liberror-perl libauthen-sasl-perl
  libemail-valid-perl libio-socket-ssl-perl libnet-smtp-ssl-perl"
 
+CC_PACKAGE=
+case "$jobname" in
+linux-gcc | linux-TEST-vars)
+	CC_PACKAGE=gcc-8
+	;;
+osx-gcc)
+	CC_PACKAGE=gcc-9
+	;;
+esac
+
 case "$runs_on_pool" in
 ubuntu-latest)
 	# The Linux build installs the defined dependency versions below.
diff --git a/ci/lib.sh b/ci/lib.sh
index 8fb0bfd43e1..977ee6293ef 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -51,6 +51,9 @@ setenv () {
 	fi
 }
 
+# Clear variables that may come from the outside world.
+CC=
+
 # How many jobs to run in parallel?
 NPROC=10
 
@@ -70,8 +73,6 @@ MAKEFLAGS="$MAKEFLAGS SKIP_DASHED_BUILT_INS=$SKIP_DASHED_BUILT_INS"
 
 case "$CI_TYPE" in
 github-actions)
-	CC="${CC:-gcc}"
-
 	setenv --test GIT_PROVE_OPTS "--timer --jobs $NPROC"
 	GIT_TEST_OPTS="--verbose-log -x"
 	test Windows != "$RUNNER_OS" ||
@@ -143,9 +144,14 @@ vs-test)
 	setenv --test MAKEFLAGS "$COMMON_MAKEFLAGS"
 	;;
 linux-gcc)
+	CC=gcc
 	setenv --test GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME main
 	;;
+linux-gcc-default)
+	CC=gcc
+	;;
 linux-TEST-vars)
+	CC=gcc
 	setenv --test GIT_TEST_SPLIT_INDEX yes
 	setenv --test GIT_TEST_MERGE_ALGORITHM recursive
 	setenv --test GIT_TEST_FULL_IN_PACK_ARRAY true
@@ -160,13 +166,22 @@ linux-TEST-vars)
 	setenv --test GIT_TEST_WRITE_REV_INDEX 1
 	setenv --test GIT_TEST_CHECKOUT_WORKERS 2
 	;;
+osx-gcc)
+	CC=gcc
+	;;
+osx-clang)
+	CC=clang
+	;;
 linux-clang)
+	CC=clang
 	setenv --test GIT_TEST_DEFAULT_HASH sha1
 	;;
 linux-sha256)
+	CC=clang
 	setenv --test GIT_TEST_DEFAULT_HASH sha256
 	;;
 pedantic)
+	CC=gcc
 	# Don't run the tests; we only care about whether Git can be
 	# built.
 	setenv --build DEVOPTS pedantic
@@ -181,9 +196,11 @@ linux-musl)
 	MAKEFLAGS="$MAKEFLAGS GIT_TEST_UTF8_LOCALE=C.UTF-8"
 	;;
 linux-leaks)
+	CC=gcc
 	setenv --build SANITIZE leak
 	setenv --test GIT_TEST_PASSING_SANITIZE_LEAK true
 	;;
 esac
 
-setenv --build MAKEFLAGS "$MAKEFLAGS CC=${CC:-cc}"
+MAKEFLAGS="$MAKEFLAGS${CC:+ CC=$CC}"
+setenv --build MAKEFLAGS "$MAKEFLAGS"
-- 
2.36.0.rc2.898.gdf6bbac50ff