libhandy installs glade files outside of prefix
Noticed when building with jhbuild:
W: Files remaining in buildroot '/home/mcatanzaro/Projects/GNOME/install/_jhbuild/root-libhandy-broken'; module may have installed files outside of prefix.
Apparently I tried fixing it in the past, but failed due to glade#376 (closed). Now that is fixed, we can fix it properly.