Fix build by making the registry guarded by an ArcMutex.

src/intermediate/target.rs

@@ -9,6 +9,7 @@ pub(crate) struct ITarget {
 }
 
 intermediate!(ITarget, Target, original, registry, {
+    let mut registry = registry.lock().unwrap();
     let id = registry.get_target(original.value);
     Ok(ITarget {
         id: id.clone(),