Add buck to PATH
Add buck to PATH

Summary: As I said in D4802726, this will require a few iterations.

Reviewed By: rspencer01

Differential Revision: D4803280

fbshipit-source-id: dce005c6c8d673da0818067e4bcee36a92194182

facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho