ruby.c: no -r when dump

* ruby.c (process_options, load_file_internal2): should not
  require other files when dump option is given.
  [ruby-dev:48712] [Bug #10435]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48175 b2dd03c8-39d4-4d8f-98ff-823fe69b080e