[llvm][Demangle][NFC] Fix demangle to work with LIBCPP_REMOVE_TRANSITIVE_INCLUDES
diff --git a/llvm/include/llvm/Demangle/ItaniumDemangle.h b/llvm/include/llvm/Demangle/ItaniumDemangle.h
index acdf570..21fd95b 100644
--- a/llvm/include/llvm/Demangle/ItaniumDemangle.h
+++ b/llvm/include/llvm/Demangle/ItaniumDemangle.h
@@ -27,6 +27,7 @@
 #include <cstring>
 #include <limits>
 #include <new>
+#include <type_traits>
 #include <utility>
 
 DEMANGLE_NAMESPACE_BEGIN