Hi e-ink,
I've described the build process in
a new thread. To answer your specific question: No, I did not use the toolchain distributed by Sony (GCC 4.1.2), but the GCC 4.4.3 toolchain from a more recent Android NDK. That seemed to be a better match for the GCC 4.4.0 the shipped kernel has been compiled with (according to /proc/version).