Update cabal script environment hack for Cabal 3.8

Thanks to useful pointer from haskell/cabal#6999 (comment).

File watching actually doesn't work, as the same hash is reused for the same script (based on location?) even after edits. This is much cleaner anyway.

CabScriptWatchEnv.hs

@@ -13,36 +13,32 @@ It is the workaround mentioned [here](https://github.com/haskell/cabal/issues/69
 -}
 module CabScriptWatchEnv (main) where
 
-import Control.Concurrent
 import Control.Monad
 import Data.ByteString.Char8 (
     isPrefixOf,
-    isSuffixOf,
     lines,
     putStrLn,
     unlines,
  )
 import Data.ByteString.RawFilePath (readFile, writeFile)
+import Data.Foldable
 import RawFilePath
+import System.Exit
 import System.FilePath.ByteString
-import System.INotify
+import System.Posix.ByteString
 import Prelude hiding (lines, putStrLn, readFile, unlines, writeFile)
 
 main :: IO ()
 main = do
-    m <- newEmptyMVar
-    tmp <- getTemporaryDirectory
-    inot <- initINotify
-    void $ addWatch inot [Create] tmp \case
-        Created isDir p -> do
-            when (isDir && "cabal-repl." `isPrefixOf` p) $
-                void $ addWatch inot [MoveIn] (tmp </> p) \case
-                    MovedIn _ p' _ -> do
-                        when (".ghc.environment." `isPrefixOf` p' && not (".tmp" `isSuffixOf` p')) do
-                            putStrLn $ "Found: " <> p'
-                            putMVar m (tmp </> p </> p')
-                    _ -> pure ()
-        _ -> pure ()
-    envFile <- takeMVar m
-    contents <- readFile envFile
-    writeFile (takeFileName envFile) $ unlines $ filter (not . ("package-db dist-newstyle" `isPrefixOf`)) $ lines contents
+    p <-
+        getArgs >>= \case
+            [p] -> pure p
+            _ -> putStrLn "Provide a script-build folder" >> exitFailure
+    envFiles <- filter (".ghc.environment." `isPrefixOf`) <$> listDirectory p
+    if null envFiles
+        then putStrLn "No environment files found" >> exitFailure
+        else putStrLn "Found environment files:"
+    for_ envFiles \envFile -> do
+        putStrLn envFile
+        contents <- readFile $ p </> envFile
+        writeFile (takeFileName envFile) $ unlines $ filter (not . ("package-db dist-newstyle" `isPrefixOf`)) $ lines contents