Draft: ci: Add a pre-merge job that builds the gnome-build-meta module set
The job checks out gnome-buil-meta, opens a workspace for glib and tries to build all the elements in the Flatpak runtime, along with the GNOME Core module set against the checkout glib version.
This will help with catching breaking changes and compilation regressions that might get introduced.
By default its a manual job, that will automatically run if the merge request is assigned to Marge the merge bot.