Merge pull request #739 from netbootxyz/use_builder_image

Switches to prebuilt image for building

Dockerfile-build

@@ -1,4 +1,4 @@
-FROM ubuntu:20.04 as builder
+FROM netbootxyz/docker-builder:latest as builder
 
 ENV DEBIAN_FRONTEND=noninteractive
 

Dockerfile-build.production

@@ -1,4 +1,4 @@
-FROM ubuntu:20.04 as builder
+FROM netbootxyz/docker-builder:latest as builder
 
 ENV DEBIAN_FRONTEND=noninteractive