/usr/lib/gcc-cross/sparc64-linux-gnu/7/libgcc_s.so is in libgcc-7-dev-sparc64-cross 7.3.0-16ubuntu3cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/sparc64-linux-gnu/7/../../../../sparc64-linux-gnu/lib/libgcc_s.so.1