/usr/share/acl2-6.3/books/parallel/without-waterfall-parallelism.o is in acl2-books 6.3-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/acl2-6.3/books/parallel/../../../../lib/acl2-6.3/books/parallel/without-waterfall-parallelism.o