Attempt to fix the MSVC build.

llvm-svn: 199352
diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp
index 60adc9b..5878e59 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp
@@ -50,7 +50,9 @@
   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
   }
 
 }