Something

root@localhost:~# update-alternatives --install /usr/bin/gcc cc /usr/bin/gcc-3.4  2
root@localhost:~# update-alternatives --install /usr/bin/gcc cc /usr/bin/gcc-4.0 1
root@localhost:~# update-alternatives --config cc

There are 2 alternatives which provide `cc'.

  Selection    Alternative
-----------------------------------------------
 +    1        /usr/bin/gcc-3.4
      2        /usr/bin/gcc-4.0

Press enter to keep the default[*], or type selection number: