Partially revert a gtk-doc 1.31 change that broke e-d-s and NM builds
From: Kalev Lember <@klember>
Bug: #98
Bug: #110
Bug-Fedora: https://bugzilla.redhat.com/show_bug.cgi?id=1775560
From Fedora, via Debian. This works around #98 and #110 enough to keep existing projects building, but does not fully solve those two issues.
I'm creating this MR in a spirit of cross-distro cooperation rather than because I believe it'll be merged in its current form (it would be better to log a warning, at least).