Merge branch 'jx/ci-ubuntu-fix' into maint-2.38

Adjust the GitHub CI to newer ubuntu release.

* jx/ci-ubuntu-fix:
  ci: install python on ubuntu
  ci: use the same version of p4 on both Linux and macOS
  ci: remove the pipe after "p4 -V" to catch errors
  github-actions: run gcc-8 on ubuntu-20.04 image

diff --cc .github/workflows/main.yml
index 03d1b096a9a5ab4a2ae10edf86d98123ce95d65f,831a81f61d1fdccc6d41ebf7f4b6d41c53f15a9d..51d99a56c031cdfcc4899b93ee4927ea1dcaabb8
--- 1/.github/workflows/main.yml
--- 2/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@@ -232,15 -231,14 +231,14 @@@ jobs
            - jobname: linux-gcc
              cc: gcc
              cc_package: gcc-8
-             pool: ubuntu-latest
+             pool: ubuntu-20.04
            - jobname: linux-TEST-vars
              cc: gcc
-             os: ubuntu
              cc_package: gcc-8
-             pool: ubuntu-latest
+             pool: ubuntu-20.04
            - jobname: osx-clang
              cc: clang
 -            pool: macos-latest
 +            pool: macos-12
            - jobname: osx-gcc
              cc: gcc
              cc_package: gcc-9

diff --cc ci/install-dependencies.sh
Simple merge

diff --cc ci/lib.sh
Simple merge