Add sleep to profiling
Add sleep to profiling

Summary:
Sleep a little bit after fork to let the spawn catch up.

This improves the ability to profile short passes.

Reviewed By: kuganv

Differential Revision: D28336011

fbshipit-source-id: 448f89035e1050d5e6f23047981fefd646b1a869

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex