Update build-image.sh (#2204)
Update build-image.sh (#2204)

Use environment variables to set the cross compile
architecture. This way we don't need to use --ignore-scripts
gateway-addon-node now uses git submodules are relies on
npm scripts to get the git repository checked out properly.
moziot/gateway,moziot/gateway,mozilla-iot/gateway,mozilla-iot/gateway,mozilla-iot/gateway,mozilla-iot/gateway,mozilla-iot/gateway,moziot/gateway