/usr/lib/gcc-cross/mips-linux-gnu/6/64/libobjc.so is in lib64objc-6-dev-mips-cross 6.3.0-18cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/mips-linux-gnu/6/64/../../../../../mips-linux-gnu/lib64/libobjc.so.4