feat(third_party/bazel): Check in rules_haskell from Tweag

third_party/bazel/rules_haskell/tests/binary-with-plugin/Plugin.hs

@@ -0,0 +1,15 @@
+module Plugin (plugin) where
+
+import Control.Monad (when)
+import GhcPlugins
+import System.Process (readProcess)
+
+plugin :: Plugin
+plugin = defaultPlugin { installCoreToDos = install }
+
+install :: [CommandLineOption] -> [CoreToDo] -> CoreM [CoreToDo]
+install [arg] todo = do
+  when ('$' `elem` arg) $
+    fail "Make variable not expanded."
+  _ <- liftIO $ readProcess arg [] ""
+  return todo