Environment.GetCommandLineArgs() returns null on Project N

I cannot deduce from the code and issues whether this is expected to work or not on CoreRT or Project N (it looks like it's supposed to clone a string array that's set at startup, but the startup hook is never called.)

Whatever else, null cannot be the right result. Either something faked, something valid or PNSE.

[jkotas]

It works in CoreRT with the CoreRT toolchain. It does not work in ProjectN / UWP because of the startup code is done differently there and this part was never wired up into it.

[MichalStrehovsky]

This was taken out of #if CORERT define without actually implementing it outside of CoreRT in #1496. We should just PlatformNotSupport it under #if PROJECTN. It's irrelevant for UWP.

[MichalStrehovsky]

(Also, we should remove the graceful failure mode for "things weren't initialized" that was added in that pull request. That change makes no sense to me.)