Tried to build doxygen as a dependency, and found out that the link (http://doxygen.nl/files/doxygen-1.8.15.src.tar.gz) returns a 404.
There is currently a pending bug #242347 that updates the port to the latest version (although as I check the Doxygen website now, I see that a version newer than that has been released as of yesterday). I would advise waiting for that update to happen.
(In reply to Naram Qashat from comment #2)
While I understand that updating as per bug #242347 might solve this for now, this leads me to question if the current MASTER_SITE is guaranteed to keep the old version - could switching to Sourceforge  be a better option here?
(In reply to Guangyuan Yang from comment #3)
Perhaps it would be better to use Sourceforge as a backup for MASTER_SITES for older releases. I do not know how far back the main site's downloads go. I normally have the port updated but this update has been slow to get into the ports tree for whatever reason.
^Triage: Reporter is committer, assign accordingly.
(In reply to Fernando Apesteguía from comment #5)
No. This PR will soon be Closed - Overcome by events by PR #242347 (see also).