Well I started bisecting without specifying -system-sqlite, evrything working, and when I tested v4.8.5 to make sure it failed, it passed, so I deduced that -system-sqlite might be braking the build.
I modified the formula accordingly and tested on Leopard.
(I was build Qt by hand in the git repo on Snow with 10.5sdk)
It worked.
That's no piece of wizardry.