ci: Add "check mr" job to needs: of build jobs

So that if the former fails, build & test jobs won't run, wasting less
time & CI resources.

This requires slight tweaks to the rules: of the former job, to make
sure it always exists when the build jobs do.

Acked-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7278>
1 file changed