/usr/share/acl2-6.3/books/xdoc/ is in acl2-books 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/xdoc/all.o
/usr/share/acl2-6.3/books/xdoc/autolink.o
/usr/share/acl2-6.3/books/xdoc/base.o
/usr/share/acl2-6.3/books/xdoc/book-thms-example.o
/usr/share/acl2-6.3/books/xdoc/book-thms.o
/usr/share/acl2-6.3/books/xdoc/debug.o
/usr/share/acl2-6.3/books/xdoc/defsection-tests.o
/usr/share/acl2-6.3/books/xdoc/defxdoc-raw-impl.o
/usr/share/acl2-6.3/books/xdoc/defxdoc-raw.o
/usr/share/acl2-6.3/books/xdoc/display.o
/usr/share/acl2-6.3/books/xdoc/fmt-to-str.o
/usr/share/acl2-6.3/books/xdoc/import-acl2doc.o
/usr/share/acl2-6.3/books/xdoc/importance.o
/usr/share/acl2-6.3/books/xdoc/names.o
/usr/share/acl2-6.3/books/xdoc/parse-xml.o
/usr/share/acl2-6.3/books/xdoc/portcullis.o
/usr/share/acl2-6.3/books/xdoc/prepare-topic.o
/usr/share/acl2-6.3/books/xdoc/preprocess.o
/usr/share/acl2-6.3/books/xdoc/save-classic.o
/usr/share/acl2-6.3/books/xdoc/save-fancy.o
/usr/share/acl2-6.3/books/xdoc/sort.o
/usr/share/acl2-6.3/books/xdoc/spellcheck.o
/usr/share/acl2-6.3/books/xdoc/top.o
/usr/share/acl2-6.3/books/xdoc/topics.o
/usr/share/acl2-6.3/books/xdoc/word-wrap.o
/usr/share/acl2-6.3/books/xdoc/write-acl2-xdoc.o