I would not recommend you to mix 32 and 64. Even if you do that and develop some application then where you will install it? On 32 or on 64 bit OS?

I think you should develop and test it in the environment for which you do the development.

You can:
1. Install VB (virtual box from ORACLE/SUN, for example) and install on it GUEST OS. It is allowed to have HOST OS 64 bit and GUEST OS 32 bit.

You will have 2 independent environments – one for 64-bit development and one for 32-bit development.

2. You can reboot between 32 / 64 OS.

I prefer VB.
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Indeed you develop on 64 and when it works – transfer source code to 32 and recompile.
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With VB you can have simultaneously any combination of 32/64 UNIX1/UNIX2/Win XP/Win 7/ Mac OS /…
Just instal there the right version of Qt.

Qt Updater / Installer will work without issues on every of them.

Oh! I just want to have a 32bit Qt. Installing a new Ubuntu is a little heavy. (Did I told I’m laziest programmer ever?)
I just found this: http://jblevins.org/notes/ubuntu-chroot
will try it and come back

Thank you

OK, the VB solution was better.
Thanks.