Sometimes we make changes to langtools/ that require synchronized changes to the jdk/ repo. In the case of partial builds using -Xbootclasspath, failing to use an appropriate version of jdk can lead to confusing downstream test errors.

To ameliorate the problem, we should have a sanity test, suitably named to run early or first, to detect version issues and report them in a friendly informative way, instead of leaving developers perplexed over apparent test failures.