factor out installCabal' from installCabalBindist, to be shared with installCabalBinIsolated function

lib/GHCup.hs

@@ -470,13 +470,13 @@ installCabalBindist dlinfo ver = do
   let lInstCabal = headMay . reverse . sort $ cVers
   when (maybe True (ver >=) lInstCabal) $ liftE $ setCabal ver
 
- where
 -- | Install an unpacked cabal distribution.
 installCabal' :: (MonadLogger m, MonadCatch m, MonadIO m)
               => FilePath      -- ^ Path to the unpacked cabal bindist (where the executable resides)
               -> FilePath      -- ^ Path to install to
+              -> Version
               -> Excepts '[CopyError] m ()
-  installCabal' path inst = do
+installCabal' path inst ver = do
   lift $ $(logInfo) "Installing cabal"
   let cabalFile = "cabal"
   liftIO $ createDirRecursive' inst