StdLib: Changes needed to support XCODE5

I had to make the following changes to make this build work: >build -p AppPkg/AppPkg.dsc -a X64 -t XCODE5

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Andrew Fish <afish@apple.com>
Reviewed-by: Daryl McDaniel <daryl.mcdaniel@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16081 6f19259b-4bc3-4df7-8a09-765794883524

StdLib/LibC/StdLib/Environs.c

@@ -120,7 +120,7 @@ _Exit(int status)
   longjmp(gMD->MainExit, 0x55);     // Get out of here.  longjmp can't return 0. Use 0x55 for a non-zero value.
 
 #ifdef __GNUC__
-  __builtin__Exit(status);         /* Keep GCC happy - never reached */
+  _Exit(status);        /* Keep GCC happy - never reached */
 #endif
 }