why might I be getting a Native error= mono-io-layer-error (0) in il2cpp build

I have a line that launches a new Process()
This is for a standalone Windows build.
It works fine in editor and in mono builds, but fails in il2cpp build with

Code (CSharp):

1. Native error= mono-io-layer-error (0)

What might be causing this and how would I go about fixing it?

 

Only other thing I've been able to figure out is that it seems like it doesn't matter what program I'm trying to launch or what I set as launch arguments or in StartInfo, the error is the same.

 

This may be relevant?

https://forum.unity.com/threads/solved-il2cpp-and-process-start.533988/

 

@PraetorBlue ouch. It looks like it is relevant. The workaround there would help with Windows, but not worth it for the eventual Mac and Linux releases. Thanks for the find. I've been looking all day.