still can't express custom-setup deps

They need unix on non-windows, for Utility.Env, which Build.Configure uses,
but cabal can't express that in a custom-setup stanza.

To avoid this problem, Utility.Env would need to be moved into
unix-compat..

Utility/Env/Set.hs

@@ -1,40 +0,0 @@
-{- portable environment variables
- -
- - Copyright 2013 Joey Hess <id@joeyh.name>
- -
- - License: BSD-2-clause
- -}
-
-{-# LANGUAGE CPP #-}
-
-module Utility.Env.Set where
-
-#ifdef mingw32_HOST_OS
-import qualified System.Environment as E
-import qualified System.SetEnv
-#else
-import qualified System.Posix.Env as PE
-#endif
-
-{- Sets an environment variable. To overwrite an existing variable,
- - overwrite must be True.
- -
- - On Windows, setting a variable to "" unsets it. -}
-setEnv :: String -> String -> Bool -> IO ()
-#ifndef mingw32_HOST_OS
-setEnv var val overwrite = PE.setEnv var val overwrite
-#else
-setEnv var val True = System.SetEnv.setEnv var val
-setEnv var val False = do
-	r <- getEnv var
-	case r of
-		Nothing -> setEnv var val True
-		Just _ -> return ()
-#endif
-
-unsetEnv :: String -> IO ()
-#ifndef mingw32_HOST_OS
-unsetEnv = PE.unsetEnv
-#else
-unsetEnv = System.SetEnv.unsetEnv
-#endif