mbed-os/tools/ci_templates/library_build/build_report_table.html

<table class="sortable pane bigtable stripped-odd">
  <tr>
    <th>Toolchain</th>
  </tr>
  {% for run in build %}
  <tr>
    <td>{{run.toolchain}}</td>
  </tr>
  {% endfor %}
</table>