Is it possible to have a content type build last?

No. This capability is most frequently associated with a desire to display backlinks. Perhaps this will be possible at some point with a defer keyword/function/method.

Here’s one approach, from topic #33328:

  1. In your render hook, add data attributes to the anchor element indicating source of link (data-permalink, data-title, etc.)
  2. Build the site.
  3. Use an external script to parse (using xmllint or similar) HTML files in the publish directory, and build a JSON database of links.