Include what you use for the preparser.

src/atomicops.h

Index: src/atomicops.h
diff --git a/src/atomicops.h b/src/atomicops.h
index e2057ed0731d3bf4715a458cf6e0aece595620a7..2bce56903410d3dedf8521b1c472ce5f4884c6b9 100644
--- a/src/atomicops.h
+++ b/src/atomicops.h
@@ -1,4 +1,4 @@
-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -155,7 +155,7 @@ Atomic64 Release_Load(volatile const Atomic64* ptr);
 #include "atomicops_internals_x86_macosx.h"
 #elif defined(__GNUC__) && \
   (defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_X64))
-#include "atomicops_internals_x86_gcc.h"
+#include "atomicops_internals_x86_gcc.h"  // IWYU pragma: export
 #elif defined(__GNUC__) && defined(V8_HOST_ARCH_ARM)
 #include "atomicops_internals_arm_gcc.h"
 #elif defined(__GNUC__) && defined(V8_HOST_ARCH_MIPS)