The buildah utility is a versitile container build tool that does not require a daemon (everything is direct invocation).
See my "deep dive" for a few hands on use-cases.
Recently knative was announced. It is a project to enable the kubernetes primitives needed to build a functions-as-a-service. There are a plumbing services needed around this use-case, "build" is one of them. Building containers is largely an indepenent goal and story of "serverless" or "FaaS", but I get why they are grouped together.