[travis] fix osx build
[travis] fix osx build

Summary: Untested code didn't work, surprise!

Reviewed By: mbouaziz

Differential Revision: D13179256

fbshipit-source-id: 30a078242

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