docker build: permission denied on systems where docker group is not used

[gavanderhoorn]

Trying to run the docker/build.sh script on systems where the docker group is not used to give access to the Docker socket to all members results in the following error message being displayed:

Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Post http://%2Fvar%2Frun%2Fdocker.sock/v1.39/build?buildargs=%7B%22BUILD_VERSION%22%3A%2203%22%7D&cachefrom=%5B%5D&cgroupparent=&cpuperiod=0&cpuquota=0&cpusetcpus=&cpusetmems=&cpushares=0&dockerfile=Dockerfile&labels=%7B%7D&memory=0&memswap=0&networkmode=default&rm=1&session=a986qu72woijd4y3zh7lbp1kq&shmsize=0&t=robust-rosin%2Frosinstall_generator_time_machine%3A03&target=&ulimits=null&version=1: dial unix /var/run/docker.sock: connect: permission denied

[gavanderhoorn]

Running build.sh with sudo (obviously) fixes this, but that may not be the best way to approach this.