Only provide MS builtins when -fms-extensions is on

We already have builtins that are only available in GNU mode, so this
mirrors that.

Reviewers: rsmith

Differential Revision: http://llvm-reviews.chandlerc.com/D2128

llvm-svn: 194615
diff --git a/clang/test/CodeGen/builtin-ms-noop.cpp b/clang/test/CodeGen/builtin-ms-noop.cpp
index 42c2501..7c5068d 100644
--- a/clang/test/CodeGen/builtin-ms-noop.cpp
+++ b/clang/test/CodeGen/builtin-ms-noop.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple i686-pc-win32 -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -fms-extensions -triple i686-pc-win32 -emit-llvm %s -o - | FileCheck %s
 
 class A {
  public: