/usr/lib/gcc-cross/mips64el-linux-gnuabi64/6/libobjc.so is in libobjc-6-dev-mips64el-cross 6.4.0-17ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/mips64el-linux-gnuabi64/6/../../../../mips64el-linux-gnuabi64/lib/libobjc.so.4