gobject-introspection: g-ir-scanner linker paths need fixing, sometimes picks up system lib instead of built lib
Otherwise we might/will pick up the installed lib and not the one from the build dir, causing linker errors.
https://gitlab.gnome.org/GNOME/gobject-introspection/merge_requests/72
There might be a new stable release with the patch, it was backported IIRC.
Turns out the above-mentioned patches are not enough. Needs more investigation then.