/usr/share/doc/libgcc1-dbg-powerpc-cross is in libgcc1-dbg-powerpc-cross 1:8-20180414-1ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gcc-8-cross-base
/usr/share/doc/gcc-8-cross-base