This is supposed to be so easy. You clone the zephyr repo and the iotivity-constrained repo. Then cd to port/zephyr in the iotivity-constrained repo and type ‘make’. Only the Makefile there is quite incomplete and wrong. It sets up the board definition and the config file, then these 2 lines that point to non-existent files (assuming ZEPHYR_BASE points to the root of the cloned zephyr repo):
include ${ZEPHYR_BASE}/Makefile.inc
include $(ZEPHYR_BASE)/samples/net/common/Makefile.ipstack
There is also a Makefile in port/zephyr/src, but it can’t be run as is because it has no targets. I don’t know how that ties in either, but it also references directories in the zephyr repo that don’t exist.