mruby-dir: remove run_test.rb that is no longer used

mrbgems/mruby-dir/run_test.rb

@@ -1,27 +0,0 @@
-#!/usr/bin/env ruby
-#
-# mrbgems test runner
-#
-
-gemname = File.basename(File.dirname(File.expand_path __FILE__))
-
-if __FILE__ == $0
-  repository, dir = 'https://github.com/mruby/mruby.git', 'tmp/mruby'
-  build_args = ARGV
-  build_args = ['all', 'test']  if build_args.nil? or build_args.empty?
-
-  Dir.mkdir 'tmp'  unless File.exist?('tmp')
-  unless File.exist?(dir)
-    system "git clone #{repository} #{dir}"
-  end
-
-  exit system(%Q[cd #{dir}; MRUBY_CONFIG=#{File.expand_path __FILE__} ruby minirake #{build_args.join(' ')}])
-end
-
-MRuby::Build.new do |conf|
-  toolchain :gcc
-  conf.gembox 'default'
-  conf.enable_test
-
-  conf.gem File.expand_path(File.dirname(__FILE__))
-end