PageLink dropdown relation for linking in Layout

gistfile1.txt

<?php

class HomePage extends Page {

	private static $has_one = array(
		'PageLink' => 'SiteTree'
	);

	public function getCMSFields() {

		$fields = parent::getCMSFields();

		$fields->addFieldToTab('Root.Main', new TreeDropdownField("PageLinkID", "Page to link to", "SiteTree"), 'Content');
    
    $this->extend('updateCMSFields', $fields);
    return $fields;
	}

}

You would then use <a href="$PageLink.Link">$PageLink.Title</a> in the Layout of that page type