/usr/lib/x86_64-linux-gnu/libprotoc.so is in libprotoc-dev 2.5.0-9ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libprotoc.so.8.0.0
/usr/lib/x86_64-linux-gnu/libprotoc.so.8.0.0