If it was a regular distro you could just update it (or even a minor package), I'd say that was the way to go. However, if you google upgrading libc, you'll see lots of probs with upgrading libc on its own, so I think it's a bit dangerous to do this (though will prob try if all else fails).
I could always rebuild the toolchain from scratch with same versions, but that seems a fairly major job, given I've only just got to grips with cross-compiling...