Move __CLANG_PREREQ to folly/CPortabiilty.h

Summary: [Folly] Move `__CLANG_PREREQ` to `folly/CPortabiilty.h`.

Reviewed By: Orvid

Differential Revision: D5496372

fbshipit-source-id: 710af3d30aa8bd0e5f645beede354e3463f1bb25

folly/CPortability.h

@@ -33,6 +33,18 @@
 # endif
 #endif
 
+// portable version check for clang
+#ifndef __CLANG_PREREQ
+# if defined __clang__ && defined __clang_major__ && defined __clang_minor__
+/* nolint */
+#  define __CLANG_PREREQ(maj, min) \
+    ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
+# else
+/* nolint */
+#  define __CLANG_PREREQ(maj, min) 0
+# endif
+#endif
+
 /* Define a convenience macro to test when address sanitizer is being used
  * across the different compilers (e.g. clang, gcc) */
 #if defined(__clang__)

folly/Portability.h

@@ -247,18 +247,6 @@ constexpr bool kIsSanitizeThread = false;
 #define FOLLY_GCC_DISABLE_NEW_SHADOW_WARNINGS /* empty */
 #endif
 
-// portable version check for clang
-#ifndef __CLANG_PREREQ
-# if defined __clang__ && defined __clang_major__ && defined __clang_minor__
-/* nolint */
-#  define __CLANG_PREREQ(maj, min) \
-    ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
-# else
-/* nolint */
-#  define __CLANG_PREREQ(maj, min) 0
-# endif
-#endif
-
 /* Platform specific TLS support
  * gcc implements __thread
  * msvc implements __declspec(thread)