It would be useful if we could skip tests per OS, e.g. skip Level DB JNI tests for Solaris.

In order to achieve this, we will need a separate implementation for JUnit and TestNG (mainly because TestNG allows incorrectly spelled groups, like JUnit Categories, and JUnit fails the build on missing groups; so we can't have both).

TestNG implementation would require an AnnotationTransformer whereas JUnit a Rule. Plus proper annotations like @skipOnWindows or anything similar.