Added bundler as default gems. Revisit [Feature #12733]

* bin/*, lib/bundler/*, lib/bundler.rb, spec/bundler, man/*:
    Merge from latest stable branch of bundler/bundler repository and
    added workaround patches. I will backport them into upstream.
  * common.mk, defs/gmake.mk: Added `test-bundler` task for test suite
    of bundler.
  * tool/sync_default_gems.rb: Added sync task for bundler.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65509 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/bundler/support/sudo.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Spec
+  module Sudo
+    def self.present?
+      @which_sudo ||= Bundler.which("sudo")
+    end
+
+    def sudo(cmd)
+      raise "sudo not present" unless Sudo.present?
+      sys_exec("sudo #{cmd}")
+    end
+
+    def chown_system_gems_to_root
+      sudo "chown -R root #{system_gem_path}"
+    end
+  end
+end