Attempt to fix the MSVC build.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199352 91177308-0d34-0410-b5e6-96231b3b80d8

lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp

@@ -50,7 +50,9 @@ extern "C" {
   LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
     // The noinline and the asm prevent calls to this function from being
     // optimized out.
+#if !defined(_MSC_VER)
     asm volatile("":::"memory");
+#endif
   }
 
 }