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