[buck] do not merge empty report.json files
[buck] do not merge empty report.json files

Reviewed By: martintrojer

Differential Revision: D19371357

fbshipit-source-id: ace5e66b6

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