Using "defined" in macro causes undefined behavior.

include/v8config.h

Index: include/v8config.h
diff --git a/include/v8config.h b/include/v8config.h
index 24b0e5ff3ef64d7ff11f30d495ff7953c0bc4f61..4f4b2cd55eae9b62f60b9071e5000b7a197eb10b 100644
--- a/include/v8config.h
+++ b/include/v8config.h
@@ -5,6 +5,8 @@
 #ifndef V8CONFIG_H_
 #define V8CONFIG_H_
 
+// clang-format off
+
 // Platform headers for feature detection below.
 #if defined(__ANDROID__)
 # include <sys/cdefs.h>
@@ -230,10 +232,15 @@
 #elif defined(__GNUC__)
 
 # define V8_CC_GNU 1
-// Intel C++ also masquerades as GCC 3.2.0
-# define V8_CC_INTEL (defined(__INTEL_COMPILER))
-# define V8_CC_MINGW32 (defined(__MINGW32__))
-# define V8_CC_MINGW64 (defined(__MINGW64__))
+# if defined(__INTEL_COMPILER)  // Intel C++ also masquerades as GCC 3.2.0
+#  define V8_CC_INTEL 1
+# endif
+# if defined(__MINGW32__)
+#  define V8_CC_MINGW32 1
+# endif
+# if defined(__MINGW64__)
+#  define V8_CC_MINGW64 1
+# endif
 # define V8_CC_MINGW (V8_CC_MINGW32 || V8_CC_MINGW64)
 
 # define V8_HAS___ALIGNOF__ (V8_GNUC_PREREQ(4, 3, 0))
@@ -412,4 +419,6 @@ namespace v8 { template <typename T> class AlignOfHelper { char c; T t; }; }
 #define V8_WARN_UNUSED_RESULT /* NOT SUPPORTED */
 #endif
 
+// clang-format on
+
 #endif  // V8CONFIG_H_