GCC 15 on 10.6.8 natively on PowerPC

[barracuda156]

@iains Some good news, I built gcc master on 10.6.8 running natively on G5. No MacPorts involvement, no hacks to darwin.h anymore.
Used Xcode 3.2.6 with some Unix tools sourced from 10a190 (they could be rebuilt from source, but did not get to that yet), built gcc 10.3.0 from your tree, used that to build gcc master.

(On a side note, I can finally deal with gfortran testing.)

Anything relevant we would like to test specifically?

P. S. The OS has some things to fix, as of now. The two crucial issues are: DNS not working (so no internet) and the kernel refuses to load with more than 4 GB RAM (boot args work, so no need to pull out physical sticks).