www/elinks: Unbreak build with SPIDERMONKEY and/or PYTHON options ON
Reported by: fluffy (via ports-committers)
Approved by: Dustin Marquess <jailbird@fdf.net> (maintainer)
Fixes: 2e042381a13c (www/elinks: Update to 0.20.0)
Co-authored-by: Hiroki Tagato <tagattie@FreeBSD.org>