girepository: Export builddir typelib and GIR paths

These can then be used by a parent project if GLib is used as a Meson subproject.

In particular, GJS wants to use GLib-2.0.typelib from GLib-as-a-subproject, but doesn’t want to hardcode the path to it inside the GLib builddir.

Signed-off-by: Philip Withnall pwithnall@gnome.org

Fixes: #3244 (closed)

Closes #3244 (closed)