extend/fileutils: suppress discarded method definition warnings

Library/Homebrew/extend/fileutils.rb

@@ -43,6 +43,7 @@ module FileUtils extend self
   # The monkey-patched method here is copied directly from upstream fix.
   if RUBY_VERSION < "1.9.3" or RUBY_PATCHLEVEL < 195
     class Entry_
+      alias_method :old_copy_metadata, :copy_metadata
       def copy_metadata(path)
         st = lstat()
         if !st.symlink?
@@ -85,6 +86,7 @@ module FileUtils extend self
     system RUBY_BIN/'rake', *args
   end
 
+  alias_method :old_ruby, :ruby if method_defined?(:ruby)
   def ruby *args
     system RUBY_PATH, *args
   end