This matches with the flatpak-xdg-utils change that added flatpak
prefix to flatpak-xdg-utils versions of xdg-email and xdg-open.
With this change, we now include _both_ xdg-utils and flatpak-xdg-utils
in the module build, and overwrite the xdg-utils versions of xdg-email
and xdg-open with the flatpak-xdg-utils versions when building the
container.
Just adding the appdata to the flatpak-runtime-config wasn't sufficient -
we also have to run appstream-compose to get it in the right place for
flatpak build-bundle to find.
We need a separate repository for each runtime branch, since Bodhi always
overwrites the testing/latest tags in the repository when a build is pushed
to testing or stable.
