/usr/i686-linux-gnu/lib64/libmpx.so.0 is in lib64mpx0-i386-cross 5.5.0-12ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/i686-linux-gnu/lib64/libmpx.so.0.0.0
/usr/i686-linux-gnu/lib64/libmpx.so.0.0.0