Make sure opam folder is empty before we try to create it
Make sure opam folder is empty before we try to create it

Reviewed By: ezgicicek

Differential Revision: D21323328

fbshipit-source-id: e0522e33f

facebook/infer,facebook/infer,jvillard/infer,jvillard/infer,jvillard/infer,jvillard/infer,jvillard/infer,jvillard/infer,jvillard/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer