/usr/sparc64-linux-gnu/lib/libcilkrts.so.5 is in libcilkrts5-sparc64-cross 7.3.0-16ubuntu3cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/sparc64-linux-gnu/lib/libcilkrts.so.5.0.0
/usr/sparc64-linux-gnu/lib/libcilkrts.so.5.0.0