/usr/lib/x86_64-linux-gnu/libgadu.so is in libgadu-dev 1:1.12.2-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgadu.so.3.13.0
/usr/lib/x86_64-linux-gnu/libgadu.so.3.13.0