gnome-builder: soft-dependency on flatpak-builder

[Olav Vitters <olav vitters nl>]

Hello,

gnome-builder is meant for development. One thing to make development
easier is to minimize the steps someone needs to get started.

Please add a (soft) or hard dependency in gnome-builder on
flatpak-builder. Gnome-builder will as fallback (2.24 and newer) suggest
to install flatpak-builder via packagekit. Having this already done by
the OS/distribution would make things much easier.

The purpose of this is to make it much easier for people to get started
to contribute to GNOME. Further, with flatpak it should be much easier
for a user to determine if they bug is fixed in latest version (in case
of leaf packages).

Please see for more details:
https://blogs.gnome.org/chergert/2017/03/11/simplifying-newcomer-setup/

-- 
Regards,
Olav