/usr/share/common-lisp/systems/nibbles.asd is in cl-nibbles 20170403-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/common-lisp/systems/../source/nibbles/nibbles.asd
/usr/share/common-lisp/systems/../source/nibbles/nibbles.asd