/usr/lib/gcc/x86_64-linux-gnu/5/plugin/libcc1plugin.so.0 is in gcc-5 5.4.0-6ubuntu1~16.04.10.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc/x86_64-linux-gnu/5/plugin/libcc1plugin.so.0.0.0