hang on exit with "Experimental (.NET 4.6 Equivalent)" Scripting Runtime Version

[JeffBail]

If the Scripting Runtime Version is set to "Experimental (.NET 4.6 Equivalent)" builds will hang up on exit and if you click on the window eventually the "application is not responding" dialog comes up. When run under the Editor the application stops normally. The easy workaround is to call m_process.Kill() instead of m_process.Dispose() in FFMpegLauncher.Dispose(). I tried closing the std streams before Disposing the process, calling Process.WaitForExit and the shutdown tasks from OnApplicationQuit but none of those fixed the issue. Given that this runtime is still labelled experimental it's entirely possible that this is due to a bug in Unity.