/usr/lib/x86_64-linux-gnu/libluajit-5.1.so 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/lib/x86_64-linux-gnu/libluajit-5.1.so.2.1.0
/usr/lib/x86_64-linux-gnu/libluajit-5.1.so.2.1.0