/usr/lib/x86_64-linux-gnu/debug/libstdc++.so is in libstdc++6-7-dbg 7.3.0-16ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/debug/libstdc++.so.6.0.24
/usr/lib/x86_64-linux-gnu/debug/libstdc++.so.6.0.24