/usr/share/doc/gnat-5-arm-linux-gnueabi is in gnat-5-arm-linux-gnueabi 5.5.0-12ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gcc-5-arm-linux-gnueabi-base
/usr/share/doc/gcc-5-arm-linux-gnueabi-base