I don't think this is a bug, feels like a knowledge problem on my part, post here vs opening an issue.
I use packer on macOS all the time, I've been tasked with setting up packer on a Xenial (linux) machine.
Followed multiple instructions and I have a Xenial system with packer, vagrant, and virtualbox.
$ packer version
Packer v1.1.2
$ vagrant version
Installed Version: 1.8.1
virtualbox 5.0.40
$ PACKER_LOG=1 packer build -only=virtualbox -var 'headless=true' -force -debug windows_2016.json
==> Builds finished but no artifacts were created.
Any ideas?