Add gembox "stdlib"; make Ruby module more complex

build_config.rb

@@ -2,6 +2,7 @@ MRuby::CrossBuild.new ENV.fetch 'BUILD_NAME' do |conf|
   conf.toolchain :gcc
 
   conf.gem core: 'mruby-compiler'
+  conf.gembox 'stdlib'
 
   conf.cc.flags      <<
     '-Wall'          <<

rootfs/boot/hello.rb

@@ -1,4 +1,4 @@
-hello = 'Hello, World!'
-works = 'Ruby modules work!'
-s = [hello, works].join ' '
+hello = 'Hello, World'
+works = 'Ruby modules work'
+s = [hello, works].map { |s| "#{s}!" }.join ' '
 console_puts s