girepository: Drop libgio dependency from gdump.c
It’s not particularly necessary, and makes the build-time dependencies more complex than they need to be, as it means that to generate GLib-2.0.gir and GObject-2.0.gir, libgio.so (and its generated headers) already needs to have been built.
See discussion on #3164 (closed)
These changes need to be replicated in gobject-introspection.git before
the problem can be solved, though, as that still has its own copy of
gdump.c
(which it installs and uses).
Further changes are included to fix pspec pool initialisation during dumping.
Helps: #3164 (closed)
This MR is based on top of !3760 (merged), which needs to be merged first.
Edited by Philip Withnall