/usr/lib/gcc-cross/s390x-linux-gnu/4.9/libobjc_gc.so is in libobjc-4.9-dev-s390x-cross 4.9.3-13ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/s390x-linux-gnu/4.9/../../../../s390x-linux-gnu/lib/libobjc_gc.so.4