Make ghc-cabal's `System.Directory` import more robust

Starting with directory-1.2.5 there will be a nameclash with
`withCurrentDirectory` and `MIN_VERSION_filepath()` isn't available at
bootstrap-time with the current GHC build-system.

By using explicit import lists we avoid CPP altogether

diff --git a/utils/ghc-cabal/Main.hs b/utils/ghc-cabal/Main.hs
index 6e3e10c..6da7733 100644 (file)
--- a/utils/ghc-cabal/Main.hs
+++ b/utils/ghc-cabal/Main.hs
@@ -29,7 +29,7 @@ import qualified Data.ByteString.Lazy.Char8 as BS
 import Data.List
 import Data.Maybe
 import System.IO
-import System.Directory
+import System.Directory (setCurrentDirectory, getCurrentDirectory, doesFileExist)
 import System.Environment
 import System.Exit      (exitWith, ExitCode(..))
 import System.FilePath