Clean up from the move to RC3 packages.

[livarcocc]

Removed the dotnet-core dependency on NuGet.Config now that we have RC3 packages in the cli-deps feed.
Re-enabled crossgen for windows now that we added JITPath to the crossgen call.

cc @eerhardt @brthor

[brthor]

Can you remove this function: private string GetCoreCLRRid() in Crossgen as part of this cleanup?

[livarcocc]

@brthor No, I can't use our regular GetRid functions because the coreclr packages don't differentiate windows versions like we do. I mean, if I use our getrid, we may get win10-x64 for instance, and we don't have a win10-x64 coreclr package. Which is why I have kept that function in place.

[livarcocc]

Windows is failing due to https://github.com/dotnet/coreclr/issues/5201.

[eerhardt]

@livarcocc - You should be unblocked by #3260.

[gkhanna79]

@livarcocc this is blocking ASP.NET from picking up crossgenned sharedFX. When do you think this will get addressed?

CC @piotrpMSFT

[eerhardt]

When do you think this will get addressed?

I'm rebasing it now, and will re-submit.

[gkhanna79]

Thanks @eerhardt - Please go ahead.