How to set the rpmbuild destination folder

I noticed rpmbuild (-bb and –buildroot options) creates the .rpm in different locations depending of what OS are you using:

• GNU/Linux Ubuntu <= 9.04: /usr/src/rpm/…
• GNU/Linux Ubuntu >= 9.10: /home/rpmbuild/…
• GNU/Linux Fedora: /usr/src/redhat/…

So how can I set manually the destination folder for all OS?