/usr/lib/gcc-cross/powerpc-linux-gnu/5/libgcc_s_64.so is in lib64gcc-5-dev-powerpc-cross 5.5.0-12ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/powerpc-linux-gnu/5/64/libgcc_s.so