/usr/lib/GNUstep/Bundles/libgnustep-art-020.bundle/libgnustep-back-020 is in gnustep-back0.20-art 0.20.1-2ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/GNUstep/Bundles/libgnustep-art-020.bundle/libgnustep-art-020