/usr/powerpc-linux-gnu/lib/debug/libstdc++.so.6 is in libstdc++6-4.9-dbg-powerpc-cross 4.9.3-13ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/powerpc-linux-gnu/lib/debug/libstdc++.so.6.0.20