There is a reported problem in rebuilding the Developer's Kit using IBM native tools. (This problem does not crop up if you use GCC to rebuild the tools.)
On the RS/6000, XLC version 1.3.0.0 miscompiles `jump.c'. XLC version 1.3.0.1 or later fixes this problem. You can obtain XLC version 1.3.0.2 by requesting PTF 421749 from IBM. See section `Rebuilding From Source' in Rebuilding From Source.