/usr/mips-linux-gnu/lib32/librt.so.1 is in libc6-mipsn32-mips-cross 2.23-0ubuntu3cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/mips-linux-gnu/lib32/librt-2.23.so
/usr/mips-linux-gnu/lib32/librt-2.23.so