gnome-disk-utility: fix unpackaged files

* WARNING: QA Issue: gnome-disk-utility: Files/directories were installed but not shipped
  /usr/lib/nautilus/extensions-2.0/libnautilus-gdu.la
  /usr/lib/nautilus/extensions-2.0/libnautilus-gdu.a
  /usr/lib/nautilus/extensions-2.0/.debug
  /usr/lib/nautilus/extensions-2.0/.debug/libnautilus-gdu.so

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>