Test build is dozens of gigabytes and millions of files (yeah, we have some suboptimality in how we set up bazel...), so even simple "rm -rf" can take 30+ minu

Test build is dozens of gigabytes and millions of files (yeah, we have some suboptimality in how we set up bazel...), so even simple "rm -rf" can take 30+ minutes. Docker really has too high overhead for this, especially in the cleanup stage.