gitlab: don't fail cirrus CI jobs when credits are exhausted

gitlab: don't fail cirrus CI jobs when credits are exhausted

In the last week of the month we have often run out of credits on
Cirrus CI, which causes the jobs to fail, in turn causing the
overall pipeline to fail.

The cirrus-run tool can now detect the "out of credits" scenario
and exits with a code of '3'.  We can tell gitlab to treat this
exit code as special and mark the job as "warning" instead of
"failed". This allows the pipeline status overall to remain
green, when we have non-technical issues with Cirrus CI.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20241204194807.1472261-2-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>