CI: Switch down to GCC 12, the ubuntu-latest image is not consistently

an Ubuntu 24.04 environment yet, this version should be available in
both the -22.04 and -24.04 images.

Github: closes #497


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1922412 13f79535-47bb-0310-9956-ffa450edef68

.github/workflows/linux.yml

@@ -67,11 +67,11 @@ jobs:
             env: |
               TEST_ARGS=-order=random
           # -------------------------------------------------------------------------
-          - name: GCC 14 maintainer-mode w/-Werror, install + VPATH
+          - name: GCC 12 maintainer-mode w/-Werror, install + VPATH
             config: --enable-mods-shared=reallyall --enable-maintainer-mode
             notest-cflags: -Werror -O2
             env: |
-              CC=gcc-14
+              CC=gcc-12
               TEST_VPATH=1
               TEST_INSTALL=1
               SKIP_TESTING=1