On the host:
git clone https://salsa.debian.org/vineetgarc/rebootstrap.git
cd rebootstrap
docker run --privileged --rm -it -v $PWD:/host debian:stretch /bin/bash
In the container:
apt-get update && apt-get install -y pbuilder
pbuilder create
cd /host && time pbuilder --execute bootstrap.sh HOST_ARCH=arc