/usr/lib/gcc-cross/powerpc64le-linux-gnu/4.8/libobjc_gc.so is in libobjc-4.8-dev-ppc64el-cross 4.8.2-16ubuntu4cross0.4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/powerpc64le-linux-gnu/4.8/../../../../powerpc64le-linux-gnu/lib/libobjc_gc.so.4