Remove libraries/ifBuildable.hs; it's no longer used

libraries/ifBuildable.hs

--- Returns exitcode 0 if the given package is buildable or is a boot package,
--- and 1 otherwise.
-
-module Main (main) where
-
-import Control.Monad
-import System.Directory
-import System.Environment
-import System.Exit
-import System.IO
-
-main :: IO ()
-main = do args <- getArgs
-          case args of
-              [packagesFile, package] ->
-                  doit packagesFile package
-              _ ->
-                  error "Syntax: ifBuildable <packages-file> <package>"
-
-doit :: FilePath -> String -> IO ()
-doit packagesFile package
- = do setCurrentDirectory package
-      unbuildable <- doesFileExist "unbuildable"
-      if not unbuildable
-         then exitWith ExitSuccess
-         else do mustBeBuildables <- getMustBeBuildables packagesFile
-                 if package `elem` mustBeBuildables
-                     then exitWith ExitSuccess
-                     else do hPutStrLn stderr "Warning: Package is unbuildable"
-                             exitWith (ExitFailure 1)
-
-getMustBeBuildables :: FilePath -> IO [String]
-getMustBeBuildables packagesFile
- = do xs <- readFile packagesFile
-      let nonCommentLines = filter (("#" /=) . take 1) $ lines xs
-          requiredLines = filter ((3 == ) . length) $ map words nonCommentLines
-          requiredLibraries = [ x | 'l':'i':'b':'r':'a':'r':'i':'e':'s':'/':x
-                                    <- map head requiredLines ]
-      return $ filter ("editline" /=) requiredLibraries
-