Unable to properly debug a netstandard project when starting a external executable

_From @Barsonax on May 29, 2018 14:23_

### Summary

Debugging doesnt seem to work properly when you start a net framework exe from a netstandard project through the Debug Launch setting. Everything else seems to be working fine.

When testing inside a game engine called duality I noticed this behavior. Latter on I found out that I can reproduce this in a separate project as well.

Some background info: In duality you add functionality through plugins which currently are portable projects. We want to eventually change this to netstandard projects. Plugins themselves are not runnable but instead we run duality itself when you try to run a plugin in VS. This will load all the plugins so you can proceed to debugging your plugin.

Note: the attached test project was simplified as much as possible to isolate the problem and thus does not include duality.

### How to reproduce

- Download and open the attached test project.
- RebuildBuild the solution and start `ClassLibrary1`. This will actually start the exe generated by `NetStandardDebugTest`. Note that it will run properly.
- Now set a breakpoint and run it again. Note that the break point will not work.
- Now try to pause the execution. You will get a Unknown error 0x80004005

### Attachments

- [NetStandardDebugTest.zip](https://github.com/AdamsLair/duality/files/2048379/NetStandardDebugTest.zip)

_Copied from original issue: dotnet/standard#760_