/usr/lib/x86_64-linux-gnu/libopenlibm.so is in libopenlibm-dev 0.5.4+dfsg-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libopenlibm.so.2.3
/usr/lib/x86_64-linux-gnu/libopenlibm.so.2.3