Fix condition to use clang in MSVS
#include <stdio.h>
#include <stdlib.h>
-#if 1
+#include <__config>
+
+#ifdef _LIBCPP_COMPILER_MSVC
// We don't want to depend on MSVC headers but
// we have conflicting definitions otherwise due to
// some other dependency on eh.h.
-#include <__config>
#include _LIBCPP_MSVC_INCLUDE(eh.h)
#else
