/usr/mipsel-linux-gnu/lib32/debug/libstdc++.so.6 is in libn32stdc++6-5-dbg-mipsel-cross 5.5.0-12ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/mipsel-linux-gnu/lib32/debug/libstdc++.so.6.0.21