concurrent docker builds on Google Container Builder

cloudbuild.yaml

steps:
- name: 'gcr.io/cloud-builders/docker'
  args:
  - 'build'
  - '-f'
  - 'Dockerfile.alpine'
  - '-t'
  - 'gcr.io/$PROJECT_ID/large-docker-alpine:latest'
  - '.'
  waitFor: ['-']
- name: 'gcr.io/cloud-builders/docker'
  args:
  - 'build'
  - '-f'
  - 'Dockerfile.ubuntu'
  - '-t'
  - 'gcr.io/$PROJECT_ID/large-docker-ubuntu:latest'
  - '.'
  waitFor: ['-']

images:
- 'gcr.io/$PROJECT_ID/large-docker-alpine:latest'
- 'gcr.io/$PROJECT_ID/large-docker-ubuntu:latest'