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
gvc has made some recent changes that rename its user options
following meson guidelines for GNOME packages[0].
The options used in gvc as a subproject have been renamed
accordingly.
[0] https://wiki.gnome.org/Initiatives/GnomeGoals/MesonPorting
Meson is on track to replace autotools as the build system of choice,
so support it in addition to autotools. If all goes well, we'll
eventually be able to drop the latter ...
https://bugzilla.gnome.org/show_bug.cgi?id=783229
When using the meson build system, gvc will be built as a subproject.
As meson restricts submodules to a subprojects/ directory in the
source tree root, move the submodule there.
https://bugzilla.gnome.org/show_bug.cgi?id=783229
