This commit adds a 'dependencies' keyword to the
gnome.compile_resources() function, which allows your resource blob
to depend on files generated at build-time from custom_target() or
configure_file() targets.
My current use case for this is source data that gets processed with Gettext
translation tools before being compiled into the resource blob.
This feature only works with GLib version 2.48.2 and above. So the
compile_resources() function now detects GLib version and raises an
error if the version of GLib being used is too old.
The compile_resources() test case is now split into two, so that the
existing one can continue to run on systems with old GLib versions (such
as Ubuntu Xenial, which the automated tests on travisci.org use), but
where new enough GLib is available we also test generating gresource
content.
The existing warning about glib-compile-resources is now only printed
if GLib version is older than 2.50.0 because
<https://bugzilla.gnome.org/show_bug.cgi?id=745754> is fixed in the
2.50.0 release.