<ul class="mobile-nav">
  <li class="mobile-nav__item">
    <a class="mobile-nav__link" href="#primary-nav">Menu</a>
  </li>

  <li class="mobile-nav__item">
    <a class="mobile-nav__link mobile-nav__link--search" href="#search-bar">
      <span class="icon icon--search-white"></span>
      <span class="visually-hidden">Search</span>
    </a>
  </li>
</ul>

<ul class="mobile-nav">
  <li class="mobile-nav__item">
    <a class="mobile-nav__link" href="#primary-nav">Menu</a>
  </li>
  <% unless defined? @dont_show_search_box %>
    <li class="mobile-nav__item">
      <a class="mobile-nav__link mobile-nav__link--search" href="#search-bar">
        <span class="icon icon--search-white"></span>
        <span class="visually-hidden">Search</span>
      </a>
    </li>
  <% end %>
</ul>

Add conditional ruby code to the mobile nav
Add conditional ruby code to the mobile nav
