/usr/lib/gcc/x86_64-linux-gnu/4.8/x32/libstdc++.so is in libx32stdc++-4.8-dev 4.8.5-4ubuntu8.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc/x86_64-linux-gnu/4.8/x32/../../../../../libx32/libstdc++.so.6