On QNX the process spawning is done by sending a message to the userspace process manager, which creates a new process table entry and queues up its initial thread. When its initial thread gets a timeslice its entry point may be the dynamic loader (as specified in the PT_INTERP segment) which then does all the dynamic linking as the spawned process or it might be some other entry point like with a statically-linked executable.

So on QNX, the spawned process does all the dynamic linking. The spawning process just sends an asynchronous message to the process manager and then gets on with things in a very deterministic manner as befitting a hard realtime system.