Help IWYU understand headers.

Change-Id: Ieaa9e70d566b759d9c3664381bc5a6ab48c2575f
diff --git a/aos/events/event_loop.h b/aos/events/event_loop.h
index 6ffb0fe..dc458e7 100644
--- a/aos/events/event_loop.h
+++ b/aos/events/event_loop.h
@@ -753,6 +753,6 @@
 
 }  // namespace aos
 
-#include "aos/events/event_loop_tmpl.h"
+#include "aos/events/event_loop_tmpl.h"  // IWYU pragma: export
 
 #endif  // AOS_EVENTS_EVENT_LOOP_H