Make --clean work
Make --clean work

Summary:
It's a documented option but it never actually gets parsed. This fixes
that and makes redexdump's output more diffable.

Reviewed By: dariorussi

Differential Revision: D3409906

fbshipit-source-id: fe280f675710872f86670d3d4c9d9776e42f7c56

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