The version of manifest-tool in `weshigbee/manifest-tool` is version
0.3.0 and is erroring on every build; latest is 0.8.0 and doesn't error.
Since we are no longer limited to what will run in a container at
CircleCI, also build all architectures.
Run build, lint and unit-test steps in a container, using a pre-built
image to save rebuilding at CircleCI
Move a couple of scripts up to config.yml for clarity