/usr/mips64-linux-gnuabin32/lib/librt.so.1 is in libc6-mipsn32-cross 2.27-3ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/mips64-linux-gnuabin32/lib/librt-2.27.so
/usr/mips64-linux-gnuabin32/lib/librt-2.27.so