/usr/lib/gcc-cross/powerpc64-linux-gnu/6/libgomp.so is in libgcc-6-dev-ppc64-cross 6.4.0-17ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/powerpc64-linux-gnu/6/../../../../powerpc64-linux-gnu/lib/libgomp.so.1