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

infer/lib/clang_wrappers/clang_wrapper

@@ -39,4 +39,11 @@ done
 # compiler can't elevate them to error level.
 COMMAND+=("-Wno-everything")
 
+
+# set _FORTIFY_SOURCE to 0 to prevent it from changing some function prototypes
+# https://securityblog.redhat.com/2014/03/26/fortify-and-you/
+# We always do it when building models so we should do same thing
+# when building any source code
+COMMAND+=("-D_FORTIFY_SOURCE=0")
+
 "${COMMAND[@]}"