Include the intrin header before using intrinsics on MSVC

Summary: The tests that would have caught this aren't currently in the CMake file, but this is needed before trying to use the intrinsics here.

Reviewed By: yfeldblum

Differential Revision: D9952025

fbshipit-source-id: 40c7034ef7e0877ccb95525fa09ab46a3526af0b

folly/synchronization/AtomicUtil-inl.h

@@ -25,6 +25,10 @@
 #include <tuple>
 #include <type_traits>
 
+#if _WIN32
+#include <intrin.h>
+#endif
+
 namespace folly {
 namespace detail {