/usr/lib/x86_64-linux-gnu/librpmbuild.so.3 is in librpmbuild3 4.11.1-3ubuntu0.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/librpmbuild.so.3.2.0
/usr/lib/x86_64-linux-gnu/librpmbuild.so.3.2.0