Help IWYU understand headers.

Change-Id: Ieaa9e70d566b759d9c3664381bc5a6ab48c2575f
diff --git a/aos/configuration.h b/aos/configuration.h
index f1bcece..5579334 100644
--- a/aos/configuration.h
+++ b/aos/configuration.h
@@ -8,7 +8,7 @@
 
 #include <string_view>
 
-#include "aos/configuration_generated.h"
+#include "aos/configuration_generated.h"  // IWYU pragma: export
 #include "aos/flatbuffers.h"
 
 namespace aos {