ci: Add a release build with -Werror enabled.

This will keep us from needing new MRs to fix up release build warnings
after the fact.  I've mostly derived from meson-gallium, dropping
components that aren't clean yet.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6462>
1 file changed