/usr/lib/x86_64-linux-gnu/libGL.so is in libgl1-mesa-dev-lts-raring 9.1.4-0ubuntu0.1~precise2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/mesa/libGL.so
/usr/lib/x86_64-linux-gnu/mesa/libGL.so