/usr/share/doc/gfortran-7-aarch64-linux-gnu is in gfortran-7-aarch64-linux-gnu 7.3.0-16ubuntu3cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gcc-7-aarch64-linux-gnu-base
/usr/share/doc/gcc-7-aarch64-linux-gnu-base