Add Haskell::Cabal#cabal_clean_lib back to compat.

We shouldn't have removed this DSL method without a compat fallback.

Closes Homebrew/homebrew#48479.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Library/Homebrew/compat.rb

@@ -10,3 +10,4 @@ require "compat/download_strategy"
 require "compat/keg"
 require "compat/pathname"
 require "compat/dependency_collector"
+require "compat/language/haskell"

Library/Homebrew/compat/language/haskell.rb

@@ -0,0 +1,10 @@
+module Language
+  module Haskell
+    module Cabal
+      def cabal_clean_lib
+        # avoid installing any Haskell libraries, as a matter of policy
+        rm_rf lib
+      end
+    end
+  end
+end