Don't make ids for empty output tokens

byg/src/DependencyGenerator.hs

@@ -76,9 +76,7 @@ runFunctionIO :: FunctionIO -> Token a -> DepGenM' b
 runFunctionIO f input = genDependency (makeDependency input (FunctionIO f))
 
 runFunctionIO' :: FunctionIO -> Token a -> DepGenM ()
-runFunctionIO' f input = do
-  _ <- runFunctionIO f input
-  pure ()
+runFunctionIO' f input = tellDep $ makeDependency input (FunctionIO f) NoToken
 
 mapDepGenM :: (Token a -> DepGenM' b) -> Token [a] -> DepGenM' [b]
 mapDepGenM f input = genDependencyM $ \target -> do