libs/kaptan-mavlink: fix invalid dialect bug

Signed-off-by: Onur Özkan <work@onurozkan.dev>

libs/kaptan-mavlink/src/lib.rs

@@ -5,7 +5,9 @@
 /// Supported MAVLink message types for Kaptan.
 pub mod message {
     pub use mavlink::MAVLinkV2MessageRaw;
+    pub use mavlink::MavHeader;
     pub use mavlink::dialects::common::*;
 
+    #[cfg(kaptan_has_messages)]
     include!(concat!(env!("OUT_DIR"), "/mod.rs"));
 }