[Development] Correct way to create Qt5's doc when packaging from submodules sources.

[Oswald Buddenhagen]

On Tue, Jun 04, 2013 at 03:13:22PM -0300, Lisandro Damián Nicanor Pérez Meyer wrote:
> We are compiling everything from the submodules tarballs, as it makes
> maintainance much easier.
> 
i have bad news for you ...

the full qt doc generation is a two-pass process which only works with
the aggregate source tree. otherwise forward references don't work.

in principle it should be possible to do the reference validation only
after everything has been built, but that's not how qdoc & co. currently
work, and it would be a bit annoying for the doc writers, so the system
would need to support both early and delayed link validation.
also, automatic generation of cross-module class hierarchy diagrams
would become *really* challenging, if we ever tried it ...