Set _FORTIFY_SOURCE to 0 when compiling with clang
Set _FORTIFY_SOURCE to 0 when compiling with clang

Summary:public
When compiling projects with this macro set to 1 (which is default on my mac),
infer couldn't get specs for some calls. They were replaced with
different functions by preprocessor.

Reviewed By: ddino

Differential Revision: D2944618

fb-gh-sync-id: df8b457
shipit-source-id: df8b457

blzq/infer,ropas/infer,jsachs/infer,kageiit/infer,facebook/infer,kstreee/infer,ropas/infer,blzq/infer,facebook/infer,kageiit/infer,jsachs/infer,xennygrimmato/infer,xennygrimmato/infer,blzq/infer,kageiit/infer,jsachs/infer,facebook/infer,jvillard/infer,jsachs/infer,jvillard/infer,blzq/infer,kstreee/infer,facebook/infer,facebook/infer,kageiit/infer,kstreee/infer,xennygrimmato/infer,ryoon/infer,facebook/infer,jvillard/infer,ryoon/infer,kageiit/infer,jsachs/infer,ryoon/infer,xennygrimmato/infer,kstreee/infer,kstreee/infer,jvillard/infer,jsachs/infer,blzq/infer,facebook/infer,ropas/infer,xennygrimmato/infer,xennygrimmato/infer,kstreee/infer,blzq/infer,kageiit/infer,jvillard/infer,ryoon/infer,ropas/infer,ropas/infer,ryoon/infer,kageiit/infer,xennygrimmato/infer,ropas/infer,jvillard/infer,jvillard/infer,ryoon/infer