Point to the right repo, now that GLib is on GitLab, instead of relying on the redirection.
With these changes gtk+ builds for me using fallbacks for all libraries with fallbacks available. Needs the following changes: https://github.com/ebassi/graphene/pull/109 (graphene) https://bugzilla.gnome.org/show_bug.cgi?id=787414 (pango) https://github.com/mesonbuild/meson/pull/2291 (will be in meson 0.42.1) https://bugzilla.gnome.org/show_bug.cgi?id=787416