/usr/lib/x86_64-linux-gnu/libpoldiff.so is in libpoldiff-dev 3.3.8-3ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libpoldiff.so.1.3.3
/usr/lib/x86_64-linux-gnu/libpoldiff.so.1.3.3