.gitlab-ci.yml: Include the actual command used by gitlab

Someone who finds gitlab mysterious will have no idea what $CI_JOB_NAME
should be, if they wanted to reproduce the autobuild job manually. It
should be trivial to include the actual command being run in the logs.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
