/usr/lib/gcc-cross/mips-linux-gnu/5/libobjc.so is in libobjc-5-dev-mips-cross 5.3.1-14ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/mips-linux-gnu/5/../../../../mips-linux-gnu/lib/libobjc.so.4