Merge branch 'ab/ci-use-macos-12'

CI fix.

* ab/ci-use-macos-12:
  CI: upgrade to macos-12, and pin OSX version

.github/workflows/main.yml

@@ -238,11 +238,11 @@ jobs:
             pool: ubuntu-20.04
           - jobname: osx-clang
             cc: clang
-            pool: macos-latest
+            pool: macos-12
           - jobname: osx-gcc
             cc: gcc
             cc_package: gcc-9
-            pool: macos-latest
+            pool: macos-12
           - jobname: linux-gcc-default
             cc: gcc
             pool: ubuntu-latest

ci/install-dependencies.sh

@@ -30,7 +30,7 @@ ubuntu-*)
 		cp git-lfs-$LINUX_GIT_LFS_VERSION/git-lfs .
 	popd
 	;;
-macos-latest)
+macos-*)
 	export HOMEBREW_NO_AUTO_UPDATE=1 HOMEBREW_NO_INSTALL_CLEANUP=1
 	# Uncomment this if you want to run perf tests:
 	# brew install gnu-time

ci/lib.sh

@@ -252,7 +252,7 @@ ubuntu-*)
 	GIT_LFS_PATH="$HOME/custom/git-lfs"
 	export PATH="$GIT_LFS_PATH:$P4_PATH:$PATH"
 	;;
-macos-latest)
+macos-*)
 	if [ "$jobname" = osx-gcc ]
 	then
 		MAKEFLAGS="$MAKEFLAGS PYTHON_PATH=$(which python3)"