It depends on which rpm based distro you are using.
In Opensuse, the compiled rpm will end up in /usr/src/packages/RPMS
In RedHat, I think in will be in /usr/src/redhat/RPMS.
Other RedHat based distros such as Fedora and CentOS will be something similar.
I have no idea about Mandriva or other rpm distros except to say that the compiled rpm will be somewhere in /usr/src.
You will find out the file name when you find it in /usr/src/..../RPMS.