[Tracker] Incomplete introspection data for libtracker-sparql

[Sam Thursfield <ssssam gmail com>]

Hi
While doing the Meson conversion I noticed the GObject-introspection
data for libtracker-sparql is actually incomplete. We use the valac
`--gir` option to generate it, which means that the C parts
(tracker-resource and tracker-notifier mainly) are missed out.

You can demonstrate this in Python for example:

     $ python3
     > from gi.repository import Tracker
     > s = Tracker.SparqlBuilder()   # no problem here
     > r = Tracker.Resource()
     AttributeError: 'gi.repository.Tracker' object has no attribute 'Resource'

I'm not really sure if there's an easy way to fix this. In the
Autotools build we could perhaps run gir-scanner across the generated
.c files. Meson doesn't expose the generated .c files currently, so it
would be harder still there.
Sam