I just tried to compile this platform for my Zigbit mote (AT86RF230) here in a hello-world example, but it didn't work.
I reviewed this makefile and found that the request to compile "frame.c" was not necessary and bring up a missing error:
"make: *** No rule to make target `obj_avr-zigbit/frame.o', needed by `contiki-avr-zigbit.a'. Stop."
Frame.c is already inserted in radio's makefile.
Another problem was the undefined reference created by the missing module "core/net":
"contiki-avr-zigbit.a(sicslowpan.o): In function `input':"
"contiki/examples/hello-world/../../core/net/ipv6/sicslowpan.c:1521: undefined reference to `link_stats_input_callback'"
Both solved now. Hope it helps anyone else.