The 'check-patch' and 'check-dco' jobs only need Python and git for
checking the patches, so it's not really necessary to use a container
here that has all the other build dependencies installed. By using a
lightweight Alpine container, we can improve the runtime here quite a
bit, cutting it down from ca. 1:30 minutes to ca. 45 seconds.

Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220516082310.33876-1-thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>