Run tests with JNI checks enabled

[lptr]

There is a thing in Android called CheckJNI that wraps JavaVM and JNIEnv in decorators that do some extensive checking: https://developer.android.com/training/articles/perf-jni.html#extended-checking

It would be great if we could enabled checks like this.

[lptr]

@gavra0 suggested that we might try the -Xcheck:jni flag that is supposed to enable similar functionality - https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/clopts002.html