The following patch is taken from the debian qemu_0.8.0-1.diff meta patch. In combination with the other patches already in portage it allows qemu to be built on ppc with gcc4.
Created attachment 90586 [details, diff] patches ppc.ld for _SDA_BASE missing error
The diff does not apply cleanly to qemu-softmmu, so I copied ppc.ld from qemu-user. Am not sure why the two versions are different as both use qemu-0.8.1 for source.
Looks saner that hacking base value as we are doing right now, still, are you sure the gcc4 built qemu works then?
patch applied, I reject the gcc4 claims for now.