Toolchain libraries aren't target-specific

[tornewuff]

libgcc and newlib get built for generic ARM, without any machine-specific CFLAGS. It would be nice if it could optimise them for the machine being used, but this would make them machine-specific and the structure and docs would need updating to match.

This is particularly relevant for the raspberry pi port, which won't be able to use the hardfloat ABI otherwise.