build images faster using buildkit

[kkourt]

Current image builds are slowed down because there is no /dev/kvm in the build container. docker build does not support this, but buildkit does.

new dockerfile:

--- dockerfiles/root-images     2022-08-16 15:37:33.772545638 +0200
+++ dockerfiles/root-images-insecure    2022-08-16 15:37:18.772581443 +0200
@@ -1,8 +1,9 @@
+# syntax = docker/dockerfile:experimental
 # vim: set ft=dockerfile:
 FROM quay.io/lvh-images/root-builder AS builder
 COPY _data /data
 # mmdebstrap outputs messages in stderr, so we redirect stderr
-RUN lvh images build --dir /data 2>&1
+RUN --security=insecure lvh images build --dir /data 2>&1
 RUN zstd --compress --rm --threads=0 /data/images/*.qcow2
 
 # Can't use scratch here because we use `docker create` elsewhere, and

Steps:

$ docker buildx create --driver docker-container --name local --buildkitd-flags '--allow-insecure-entitlement security.insecure' --driver-opt image=moby/buildkit:master --use
$ docker buildx build --allow security.insecure . -f dockerfiles/root-images-insecure

This leads to x2 faster build on my laptop.

Links:

• security=insecure does not automatically provide access to devices docker/buildx#220
• docker build should support privileged operations moby/moby#1916