Robert P. J. DAY says:

apparently, the patchset for gcc 4.2.1 applies properly to the
source for gcc 4.2.2 and gcc 4.2.3. so, if you want, you can simply
add support for those last two just by augmenting menuconfig and
adding a couple symlinks for those two directories. seems like a
cheap way to add a couple new versions.

 # Compute x86_64-specific values

 CT_DoArchValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}"

 }