gobject-introspection: use targetOffset to look for libraries for target

fixes it finding the build and target gobject-introspection when it should only find the
target gobject-introspection

pkgs/development/libraries/gobject-introspection/setup-hook.sh

···
     fi
 }
 
-addEnvHooks "$hostOffset" make_gobject_introspection_find_gir_files
+addEnvHooks "$targetOffset" make_gobject_introspection_find_gir_files
 
 giDiscoverSelf() {
     if [ -d "$prefix/lib/girepository-1.0" ]; then