/usr/lib/gcc-cross/mips64-linux-gnuabi64/6/n32/libgcc_s.so.1 is in libn32gcc-6-dev-mips64-cross 6.4.0-17ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc-cross/mips64-linux-gnuabi64/6/n32/../../../../../mips64-linux-gnuabi64/lib32/libgcc_s.so.1