bashbrew-arch   variants
arm32v6  alpine
arm32v7  default,onbuild,slim,stretch
arm64v8  default,alpine,onbuild,slim,stretch
amd64    default,alpine,onbuild,slim,stretch
i386     default,alpine,onbuild,slim,stretch
ppc64le  default,alpine,onbuild,slim,stretch
s390x    default,alpine,onbuild,slim,stretch