/usr/sh4-linux-gnu/lib/libstdc++.so.6 is in libstdc++6-sh4-cross 8-20180414-1ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/sh4-linux-gnu/lib/libstdc++.so.6.0.25
/usr/sh4-linux-gnu/lib/libstdc++.so.6.0.25