Well, I 've added it in the build. wxSmith builds when configure runs with --enable-contrib.
I got to tell you: it works SWEET
Btw, a minor bug I noticed is that in the generated header you add all #includes for widgets inside a #ifndef WX_PRECOMP block. This doesn't work for me (not in windows, not in linux) and compile fails.
This check is not needed anyway, because if the precompiled header has been used, files belonging in it will not be used whether you guard them or not.
In case it's not clear, take your tutorial, add a wxTreeCtrl and try to compile