Inside Google we do that as well, but it's actually distinct from bazel. Bazel is a build language, and I believe they provide a reference implementation. It's not unimaginable (and as I mentioned, it has been done internally) to use caching, incremental, distributed builds. In fact, it was originally designed with those goals in mind.
What difference does that make? I am not saying you could replace this tool with sjavac, but as they both tout speed as their main feature (and justification), I am wondering whether they both employ the same techniques or different ones.