/usr/lib/gcc-cross/powerpc64-linux-gnu/5/libitm.so is in libgcc-5-dev-ppc64-cross 5.3.1-14ubuntu2cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/powerpc64-linux-gnu/5/../../../../powerpc64-linux-gnu/lib/libitm.so.1