Drupal 8 links or where is my l() function ?
The l() function is deprecated in Drupal 8, here is a starter.
Import the URL and Link classes :
use Drupal\Core\Url;
use Drupal\Core\Link;
You have several options, but basically, you can start with an url that will be used by a link.
One of the possible implementation will be used, with the Link::fromTextAndUrl method.