Add bintest header

lib/mruby/build.rb

@@ -314,6 +314,7 @@ EOS
     end
 
     def run_bintest
+      puts ">>> Bintest #{name} <<<"
       targets = @gems.select { |v| File.directory? "#{v.dir}/bintest" }.map { |v| filename v.dir }
       targets << filename(".") if File.directory? "./bintest"
       sh "ruby test/bintest.rb#{verbose_flag} #{targets.join ' '}"

test/bintest.rb

@@ -21,6 +21,8 @@ def shellquote(s)
   end
 end
 
+print "bintest - Command Binary Test\n\n"
+
 ARGV.each do |gem|
   case gem
   when '-v'; $mrbtest_verbose = true