[EXPERIMENTAL] Added test-bundled-gems task.

`test-bundled-gems` invoke test suite of bundled gems with
  build environment.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60247 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/fetch-bundled_gems.rb

@@ -0,0 +1,17 @@
+require 'fileutils'
+
+File.readlines("#{ARGV[0]}/gems/bundled_gems").each do |gem|
+  n, v, u = gem.split
+
+  v = "v" + v
+
+  case n
+  when "minitest"
+    v = "master"
+  when "test-unit"
+    v = v[1..-1]
+  end
+
+  FileUtils.mkdir_p "#{ARGV[0]}/gems/src"
+  `#{ARGV[0]}/tool/git-refresh -C #{ARGV[0]}/gems/src --branch #{v} #{u} #{n}`
+end