misc: Updated git-commit-msg.py to print rejected commit
misc: Updated git-commit-msg.py to print rejected commit

A rejected commit is now printed to stdout. This adds an additional
level of security if the ".git/COMMIT_EDITMSG" is deleted/overwritten.

Jira: https://gem5.atlassian.net/browse/GEM5-321
Change-Id: I87d463f7c40024d68bf78705f0d02fcea9f0eeeb
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25343
Reviewed-by: Bobby R. Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>
Maintainer: Bobby R. Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5