- `make dist` requires --enable-gtk-doc --enable-introspection --with-libnm-glib
- --enable-gtk-doc requires --enable-introspection
- --with-nmcli requires either --enable-introspection or pregenerated
   settings-docs.c files from the dist tarball. It does not require
   --enable-gtk-doc.

There is a bit of a problem in that --enable-introspection requires
now xsltproc. However, gobject-introspection does itself not depend
on xsltproc. So, more correct might be a special --enable-doc argument,
that combines --enable-introspection --with-xsltproc. Anyway, that
seems to make it more complicated then it already is so just implicitly
(and surprisingly?) require xsltproc with --enable-introspection.

https://bugzilla.gnome.org/show_bug.cgi?id=775003