/usr/powerpc-linux-gnuspe/lib/libthread_db.so is in libc6-dev-powerpcspe-cross 2.23-0ubuntu3cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/powerpc-linux-gnuspe/lib/libthread_db.so.1
/usr/powerpc-linux-gnuspe/lib/libthread_db.so.1