/usr/share/doc/gcc-7-multilib-arm-linux-gnueabihf is in gcc-7-multilib-arm-linux-gnueabihf 7.3.0-16ubuntu3cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gcc-7-arm-linux-gnueabihf-base