/usr/lib/x86_64-linux-gnu/libfsosystem.so is in libfsosystem-dev 0.1.0~git20110602-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libfsosystem.so.0.0.0
/usr/lib/x86_64-linux-gnu/libfsosystem.so.0.0.0