add a way to disable all builtins, wire it up to opt's -disable-simplifylibcalls flag.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125978 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetLibraryInfo.h

@@ -55,6 +55,10 @@ public:
   void setAvailable(LibFunc::Func F) {
     AvailableArray[F/8] |= 1 << (F&7);
   }
+  
+  /// disableAllFunctions - This disables all builtins, which is used for
+  /// options like -fno-builtin.
+  void disableAllFunctions();
 };
 
 } // end namespace llvm