Pretty well! You can set up a build cluster that provides workers for any of these different platforms. Each of these platforms is identified by a different set of label values. Then you can run Bazel on your personal system to 'access' any of those platforms to run your build actions or tests.
In other words: A 'bazel test' on a Linux box can trigger the execution of tests on a BSD box.
(Full transparency: I am the author of Buildbarn, one of the major build cluster implementations for Bazel.)
In other words: A 'bazel test' on a Linux box can trigger the execution of tests on a BSD box.
(Full transparency: I am the author of Buildbarn, one of the major build cluster implementations for Bazel.)