/usr/lib/x86_64-linux-gnu/libgnarl.so is in gnat-5 5.3.1-14ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgnarl-5.so.1
/usr/lib/x86_64-linux-gnu/libgnarl-5.so.1