<ul>
{% for link in linklists.main-menu.links %}
  {% assign current_class = '' %}
  {% if link.current? %}
    {% assign current_class = 'active' %}
  {% endif %}
  <li class="{{ current_class }}" >
    <a href="{{ link.url }}">{{ link.title }}</a> 
  </li>
{% endfor %}
</ul>