/usr/share/doc/libluajit-5.1-dev/changelog.Debian.gz is in libluajit-5.1-dev 2.1.0~beta3+dfsg-5.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libluajit-5.1-dev/../libluajit-5.1-2/changelog.Debian.gz