It supports to enable frozen string literal and add `--norc` option for
  disable to `.gemrc` configuration.
  See 2.5.2 release notes for other fixes and enhancements.
  https://github.com/rubygems/rubygems/blob/a8aa3bac723f045c52471c7b9328310a048561e0/History.txt#L3

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53707 b2dd03c8-39d4-4d8f-98ff-823fe69b080e