/usr/share/man/man1/aarch64-linux-gnu-gnatxref.1.gz is in gnat-8-aarch64-linux-gnu 8-20180414-1ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man1/aarch64-linux-gnu-gnat-8.1.gz