/usr/share/doc/cpp-s390x-linux-gnu/README.Bugs is in gcc-s390x-linux-gnu 4:7.3.0-3ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/cpp-s390x-linux-gnu/../gcc-7-s390x-linux-gnu-base/README.Bugs