Simplify and speed up docker build

[imbstack]

This simplifies our usage of docker somewhat by shelling out to the cli. While I was at it, I enabled buildkit.

Old Style

$ time docker build --no-cache .      
...
 ---> 348633f6652e                                           
Successfully built 348633f6652e        
docker build --no-cache .  24.17s user 2.71s system 5% cpu 8:55.36 total

Buildkit

time  DOCKER_BUILDKIT=1 docker build --no-cache . 
...
 => exporting to image                                                                                                                                                       15.5s
 => => exporting layers                                                                                                                                                      15.5s
 => => writing image sha256:850aafb7a9881a3883fb7bfc6df9d258f4a76a9378f854ba8d328fc6be0bdfb9                                                                                  0.0s
DOCKER_BUILDKIT=1 docker build --no-cache .  3.90s user 2.43s system 4% cpu 2:20.89 total

Unscientifically this is a ~6 minute speed up.

It seems to run just fine on my dev deployment.

[djmitche]

Sounds good to me. I'm not 100% clear on why it would be faster (did it maybe have to pull the node images in the first run?) but hey, it's not slower :)

[imbstack]

It is kinda hidden but the speedup comes from setting DOCKER_BUILDKIT=1. I'm not sure what magic they've done with buildkit but it is waaay faster in my experience so far.