Part of https://gitlab.gnome.org/GNOME/Initiatives/issues/1. Allows for the installation of development bundles alongside stable versions. Related to https://gitlab.gnome.org/GNOME/gnome-calendar/issues/285
As it is, Flatpak doesn't find the file and the appstream stuff doesn't get built. https://bugzilla.gnome.org/show_bug.cgi?id=788540
https://bugzilla.gnome.org/show_bug.cgi?id=782843