/usr/share/acl2-7.2dfsg/books/build/ is in acl2-books-source 7.2dfsg-3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-7.2dfsg/books/build/cert.acl2
/usr/share/acl2-7.2dfsg/books/build/doc.lisp
/usr/share/acl2-7.2dfsg/books/build/portcullis.acl2
/usr/share/acl2-7.2dfsg/books/build/portcullis.lisp
/usr/share/acl2-7.2dfsg/books/build/test/
/usr/share/acl2-7.2dfsg/books/build/test/dollar$test$$6.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar$test$5.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar$test4.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar-test1$.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar-test1.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar-test2.foo$.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar-test2.foo.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar-test3.$bar.lisp
/usr/share/acl2-7.2dfsg/books/build/test/dollar-test3.bar.lisp
/usr/share/acl2-7.2dfsg/books/build/test/top.lisp