/usr/lib/x86_64-linux-gnu/libmpc.so is in libmpc-dev 1.0.3-1+b2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmpc.so.3.0.0
/usr/lib/x86_64-linux-gnu/libmpc.so.3.0.0