Remove diagnostic job stage after bulletproofing (hopefully) the Make…

…file

For future reference, some of the git operations in CI and the Makefile
appear to *sporadically* fail in CI because of different checked-out
repo configurations.

I modified the 'git symbolic-ref' and 'git log' operations invoked from
the Makefile to detect errors and substitute a placeholder message,
based on similar changes to the Vulkan Makefile a while back. This
(appears) to eliminate the sporadic 'fatal' messages. We may need to do
that to the 'git describe' as well.

None of this reads on the generated artifacts, except that they may or
may not contain accurate tag / commit comments.

.github/workflows/presubmit.yml

@@ -39,15 +39,6 @@ jobs:
             git config --global --add safe.directory '*'
             ls -lda . .. .git Makefile
 
-      - name: List git tag
-        run: |
-          echo Git tag:
-          git describe --tags --dirty
-          echo Git branch:
-          git symbolic-ref --short HEAD
-          echo Git commit:
-          git log -1 --format="%H"
-
       - name: Validate XML
         run: |
           make -C xml validate