Crash in output handling of SynchronousExternalProcess

[Arseniy Alekseyev]

I've had an IndexOutOfBoundsException in
org.workcraft.interop.SynchronousExternalProcess.mergeChunksToArray() called from
SynchronousExternalProcess.getOutputData().

I think this is caused by the fact that there is no effort made to ensure that the process output stream is closed before returning from the SynchronousExternalProcess.start() method.
In this case SynchronousExternalProcess.start() followed by SynchronousExternalProcess.getOutputData() can cause a read concurrent to write, which can cause all sorts of bad behaviour (from incomplete output to crashes like above).

I don't see a quick fix for this because org.workcraft.interop.ExternalProcess class does not provide means to detect or enforce the end of stream.
So, ExternalProcess will probably need modifications too.