Use createProcess instead of callExternal

Cabal/src/Distribution/Simple/Command.hs

@@ -93,8 +93,8 @@ import qualified Distribution.GetOpt as GetOpt
 import Distribution.ReadE
 import Distribution.Simple.Utils
 import System.Directory (findExecutable)
-import System.Process (callProcess)
-import System.Environment (getExecutablePath, setEnv)
+import System.Process (createProcess, CreateProcess (env), proc)
+import System.Environment (getExecutablePath)
 
 data CommandUI flags = CommandUI
   { commandName :: String
@@ -652,10 +652,7 @@ commandsRun globalCommand commands args =
         _ -> do
           mCommand <- findExecutable $ "cabal-" <> name
           case mCommand of
-            Just exec -> do
-                execPath <- getExecutablePath
-                void $ setEnv "CABAL" execPath
-                callExternal flags exec cmdArgs
+            Just exec -> callExternal flags exec cmdArgs
             Nothing -> pure $ CommandReadyToGo (flags, badCommand name)
       [] -> pure $ CommandReadyToGo (flags, noCommand)
       where
@@ -667,7 +664,8 @@ commandsRun globalCommand commands args =
 
     callExternal :: a -> String -> [String] -> IO (CommandParse (a, CommandParse action))
     callExternal flags exec cmdArgs = do
-      result <- try $ callProcess exec cmdArgs
+      execPath <- getExecutablePath
+      result <- try $ createProcess (proc exec cmdArgs) { env = Just [("CABAL", execPath)] }
       case result of
         Left ex -> pure $ CommandErrors ["Error executing external command: " ++ show (ex :: SomeException)]
         Right _ -> pure $ CommandReadyToGo (flags, CommandDelegate)