When building Xfce with sources checked out from the SVN repository, you need to have gtk-doc-tools installed even if you do not want to generate/install any library docs. This is because of the GTK_DOC_CHECK() macro in many configure.in's. I wonder if this macro in xfce4-dev-tools couldn't be optimised to gracefully fail if there are no gtk-doc-utils but without stopping the configure script. So that it detects that there are no gtk-doc-tools available and so, any API docs can't be generated. I know that compiling the SVN version isn't intended for end-users and additional dependencies are necessary. Anyway, IMO gtk-doc-tools are really not necessary and what is a much bigger problem is that e.g. on Debian, probably on Ubuntu too, gtk-doc-tools depends on many other packages[1] and especially on 'gnome-common' which is a no-go for me. I want an Xfce desktop to not use Gnome :). And I had to download about 9 or 10 megabytes of new packages to fulfil the gtk-doc-tools dependencies, that isn't much fun with an expense and slow dial-up connection :(. [1] http://packages.debian.org/etch/gtk-doc-tools
Patches welcome. I don't see this getting 'fixed', though. AFAIK, there's no way to do what you want without including gtk-doc-supplied macros in our source tree, which we don't want to do.
I don't think this is a problem anymore.