misc: Add gerrit commit message hook to pre-commit

This pre-commit hook adds the Change-ID etc. to the commit message.

Change-Id: I43b239468ab60ce1a8aaabb53dd6905819a2ce05
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/62575
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

.pre-commit-config.yaml

@@ -81,3 +81,9 @@ repos:
     language: system
     stages: [commit-msg]
     description: 'The gem5 commit message checker hook.'
+  - id: gerrit-commit-msg-job
+    name: gerrit commit message job
+    entry: util/gerrit-commit-msg-hook
+    language: system
+    stages: [commit-msg]
+    description: 'Adds Change-ID to the commit message. Needed by Gerrit.'