I tried building the nonroot-user recipe you have posted here.

it errors out with this message:
E: gnupg, gnupg2 and gnupg1 do not seem to be installed. One of them is required for this operation.

I have apt-get installed gnupg and gnupg2 on my host machine. Kali 2017.3 Rolling.
Not sure what else I should do here. I am fairly new to this.