We're going to do this in another container soon, and it would also be
nice to consolidate cmake cross setup.
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5033>