/usr/share/doc/gfortran-8-multilib-arm-linux-gnueabihf is in gfortran-8-multilib-arm-linux-gnueabihf 8-20180414-1ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gcc-8-arm-linux-gnueabihf-base