No need of requiring rbconfig, it is by-default loaded

actionpack/test/dispatch/static_test.rb

@@ -1,6 +1,5 @@
 # encoding: utf-8
 require 'abstract_unit'
-require 'rbconfig'
 require 'zlib'
 
 module StaticTests

actionview/test/actionpack/controller/layout_test.rb

@@ -1,5 +1,4 @@
 require 'abstract_unit'
-require 'rbconfig'
 require 'active_support/core_ext/array/extract_options'
 
 # The view_paths array must be set on Base and not LayoutTest so that LayoutTest's inherited

activesupport/lib/active_support/core_ext/kernel/reporting.rb

@@ -1,4 +1,3 @@
-require 'rbconfig'
 require 'tempfile'
 
 module Kernel

activesupport/lib/active_support/testing/isolation.rb

@@ -1,5 +1,3 @@
-require 'rbconfig'
-
 module ActiveSupport
   module Testing
     module Isolation

railties/lib/rails/commands/dbconsole.rb

@@ -1,7 +1,6 @@
 require 'erb'
 require 'yaml'
 require 'optparse'
-require 'rbconfig'
 
 module Rails
   class DBConsole

railties/lib/rails/commands/runner.rb

@@ -1,5 +1,4 @@
 require 'optparse'
-require 'rbconfig'
 
 options = { environment: (ENV['RAILS_ENV'] || ENV['RACK_ENV'] || "development").dup }
 code_or_file = nil

railties/lib/rails/generators/actions.rb

@@ -1,5 +1,4 @@
 require 'open-uri'
-require 'rbconfig'
 
 module Rails
   module Generators