/usr/share/common-lisp/systems/acl-compat.asd is in cl-acl-compat 1.2.42+cvs.2010.02.08-dfsg-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/common-lisp/systems/../source/cl-acl-compat/acl-compat.asd