gitlab: introduce explicit "container" and "build" stages

gitlab: introduce explicit "container" and "build" stages

If no stage is listed, jobs get put in an implicit "test" stage.
Some jobs which create container images to be used by later stages
are currently listed as in a "build" stages.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200622153318.751107-2-berrange@redhat.com>
Message-Id: <20200701135652.1366-21-alex.bennee@linaro.org>