revert the change. GF_LIB_PATH needs to be checked

Setup.hs

@@ -9,7 +9,7 @@ import System.IO.Error (catchIOError)
 import System.Exit (ExitCode(..),exitFailure)
 import System.Environment (getArgs,lookupEnv)
 import System.Process (rawSystem,readProcess)
-import System.FilePath ((</>))
+import System.FilePath ((</>),splitSearchPath)
 import System.Directory (createDirectoryIfMissing,copyFile,getDirectoryContents,removeDirectoryRecursive,findFile)
 #if __GLASGOW_HASKELL__>=800
 import System.Directory (getModificationTime,setModificationTime)
@@ -60,6 +60,7 @@ errLocation :: String
 errLocation = unlines $
   [ "Unable to determine where to install the RGL. Please do one of the following:"
   , " - Pass the " ++ destination_flag ++ "... flag to this script"
+  , " - Set the GF_LIB_PATH environment variable"
   , " - Compile & install GF from the gf-core repository"
   ]
 
@@ -118,10 +119,11 @@ mkInfo = do
   let gf = maybe default_gf id (getFlag gf_flag args)
   -- Look for install location in a few different places
   let mflag = getFlag destination_flag args
+  menvar <- lookupEnv "GF_LIB_PATH" >>= return . fmap (head . splitSearchPath)
   mbuilt <- catchIOError (readProcess gf ["--version"] "" >>= return . getPath) (\e -> return Nothing)
   let
     inst_dir =
-      case catMaybes [mflag,mbuilt] of
+      case catMaybes [mflag,menvar,mbuilt] of
         [] -> Nothing
         p:_ -> Just p
   let verbose = verbose_switch `elem` args || verbose_switch_short `elem` args