[buck] Use project_root as base for compilation data file instead of cwd
[buck] Use project_root as base for compilation data file instead of cwd

Reviewed By: dulmarod

Differential Revision: D19496545

fbshipit-source-id: 478ea4982

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