GSettings schemas are now compiled at install time, so it is no
longer necessary to include the compiled schema in the archive.
However the `gnome-extensions pack` command hasn't been adjusted,
so that it can still be used to produce valid archives for all
supported versions.
To not let that code linger forever, error out when building
a version where GNOME 44 is the oldest supported release.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2639>
Error reporting is useful when used interactively, but often undesirable
when used in scripts. Account for that with a common --quiet option,
which is more convenient than redirection stderr to /dev/null.
https://gitlab.gnome.org/GNOME/gnome-shell/issues/2391
The gnome-extensions tool code is really independent from the rest of the
code base, and could be used either as part of the gnome-shell build or as
stand-alone project (for example for the extension-ci docker image).
We can actually support both cases by moving the code to a subproject.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/877
