I don't know if you succeeded already, but it may be a little more complicated than what I wrote in my previous post.
export QTDIR=/usr/qt/4
may not be quite enough to get the compiler to use qt4. Check out the comment by marc[i1] at this link
http://aur.archlinux.org/packages.php?do_Details=1&ID=11676
There's more exporting going on there than just QTDIR.
Oh, and forget both of the "loose" qmakes that I mentioned in my previous post. Those turn out to be completely unnecessary (doesn't do any harm though).
Good luck, and if you succeed, it would be great if you posted somewhere in this forum (or the brand new wiki) how you did it.
Regards,
heyn