tools/derbyrunjartest.java doesn't use the jvmflags property when it starts a sub-process, so one cannot pass custom flags to the process. This makes it difficult to get the test to pass when running with code coverage tools.
For example, for EMMA, we need to manipulate the classpath and reduce the verbosity level. And we need to pass a -javaagent flag if we're running with JaCoCo. Using the jvmflags property works for those tests that don't spawn processes.