MRuby::Build.new do |conf|

    # ... (snip) ...

    conf.gem :github => 'genya0407/mruby-erubi'
end

hoge = '<script>while (true) { alert("This is infinit!"); }</script>'
template = '<%= hoge %>'

# You can escape HTML string by `escape` option
src = Erubi::Engine.new(template, escape: true).src
eval(src) #=> '&lt;script&gt;while (true) { alert(&quot;This is infinit!&quot;); }&lt;/script&gt;'