Write hoogle output in utf8; fixes GHC build on Windows

src/Haddock/Backends/Hoogle.hs

@@ -26,7 +26,7 @@ import Data.Char
 import Data.List
 import Data.Maybe
 import System.FilePath
-
+import System.IO
 
 prefix :: [String]
 prefix = ["-- Hoogle documentation, generated by Haddock"
@@ -42,8 +42,10 @@ ppHoogle package version synopsis prologue ifaces odir = do
                    ["@package " ++ package] ++
                    ["@version " ++ version | version /= ""] ++
                    concat [ppModule i | i <- ifaces, OptHide `notElem` ifaceOptions i]
-    writeFile (odir </> filename) (unlines contents)
-
+    h <- openFile (odir </> filename) WriteMode
+    hSetEncoding h utf8
+    hPutStr h (unlines contents)
+    hClose h
 
 ppModule :: Interface -> [String]
 ppModule iface = "" : doc (ifaceDoc iface) ++