OK, so this one is a workaround. I'm not sure what the proper fix would be.
I'd be grateful for comments on how to solve this in a better way. The mklibs.py script is stripping one symbol too much (__ctype_toupper) from the uclibc libc, which breaks busybox. This might be toolchain dependent - I've done my testing on Gnewsense Deltad (aka Ubuntu Dapper Drake) with GCC 4.1.0.
Thanks, Ward.