/usr/lib/x86_64-linux-gnu/libgailutil.so is in libgail-dev 2.24.30-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgailutil.so.18.0.1
/usr/lib/x86_64-linux-gnu/libgailutil.so.18.0.1