The gobject bindings are adequately covered in the usual manual pages:
guestfs(3). There is no need for separate generation of gtk-doc.
Also generating gtk documentation is the slowest part of the build,
and the tooling around gtk-doc is broken
(https://bugzilla.redhat.com/show_bug.cgi?id=1465665).
Note this removes the configure ‘--enable-gtk-doc’ option. Using this
option now gives a warning, but is otherwise ignored:
configure: WARNING: unrecognized options: --enable-gtk-doc