/usr/sh4-linux-gnu/lib/libm.so.6 is in libc6-sh4-cross 2.24-10cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/sh4-linux-gnu/lib/libm-2.24.so
/usr/sh4-linux-gnu/lib/libm-2.24.so