docker: split minimum setup to separate script

.dockerignore

@@ -2,3 +2,4 @@
 # with a volume.
 *
 .*
+!setup

Dockerfile

@@ -1,10 +1,5 @@
 # https://github.com/cirosantilli/linux-kernel-module-cheat#docker
 FROM ubuntu:18.04
-RUN apt update
-# Minimum requirements to run ./build --download-dependencies
-RUN apt-get install -y \
-      git \
-      python3 \
-      python3-distutils \
-    ;
+COPY setup /
+RUN /setup -y
 CMD bash

build

@@ -125,6 +125,7 @@ name_to_component_map = {
         # TODO test it out on Docker and answer that question properly:
         # https://askubuntu.com/questions/350475/how-can-i-install-gem5
         apt_get_pkgs={
+            'device-tree-compiler',
             'diod',
             'libgoogle-perftools-dev',
             'protobuf-compiler',

run

@@ -333,7 +333,7 @@ def main(args, extra_args=None):
                 ])
                 virtio_gpu_pci = []
             else:
-                virtio_gpu_pci = ['-device', 'virtio-gpu-pci']
+                virtio_gpu_pci = ['-device', 'virtio-gpu-pci', common.Newline]
             if args.arch == 'x86_64':
                 append = ['-append', '{} nopat {}'.format(root, kernel_cli), common.Newline]
                 cmd.extend([
@@ -346,7 +346,7 @@ def main(args, extra_args=None):
                     cpu = 'cortex-a15'
                 else:
                     cpu = 'cortex-a57'
-                append = ['-append', '{} {}'.format(root, kernel_cli)]
+                append = ['-append', '{} {}'.format(root, kernel_cli), common.Newline]
                 cmd.extend(
                     [
                         # highmem=off needed since v3.0.0 due to:

setup

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# Minimum requirements to run ./build --download-dependencies
+y=
+if [ $# -eq 1 ]; then
+  y=-y
+fi
+apt-get update
+apt-get install $y \
+  git \
+  python3 \
+  python3-distutils \
+;