The flatpak-info file was moved to a different location a while
ago, we should read it from there instead of relying on the
compat symlink. One advantage is that this is a fixed, short
path, we don't have to construct one dynamically.
https://bugzilla.gnome.org/show_bug.cgi?id=781826
These are private helper functions that will be used in
the following commits to get information about whether
we are running in a flatpak sandbox, etc.
We allow the use of GTK_USE_PORTAL=1 in the environment
to force the use of portals. This can be useful for
testing and debugging portal interaction.
https://bugzilla.gnome.org/show_bug.cgi?id=768498
