Fix validate: -Werror bug in patch "Replacing copyins and copyouts..."

compiler/iface/BinIface.hs

@@ -74,11 +74,6 @@ readBinIface_ checkHiWay traceBinIFaceReading hi_path nc = do
                      vcat [text "Wanted " <> ppr wanted <> text ",",
                            text "got    " <> ppr got])
 
-      errorOnMismatch' :: (Eq a, Show a) => String -> a -> a -> IO () -> IO ()
-      errorOnMismatch' what wanted got io
-           = do when (wanted /= got) $ io
-                errorOnMismatch what wanted got
-
       errorOnMismatch :: (Eq a, Show a) => String -> a -> a -> IO ()
       errorOnMismatch what wanted got
             -- This will be caught by readIface which will emit an error