/usr/lib/x86_64-linux-gnu/libgc.so is in libgc-dev 1:7.2d-5ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgc.so.1.0.3
/usr/lib/x86_64-linux-gnu/libgc.so.1.0.3