Make Arcade SDK use latest SignTool and pass new parameter to SignTool

[JohnTortugo]

I'm working on a logic to find the installed version of "sn.exe" on the machine, but for now this should work since the user can specify the path to 'sn.exe' in Signing.props.

[weshaggard]

I'm working on a logic to find the installed version of "sn.exe" on the machine, but for now this should work since the user can specify the path to 'sn.exe' in Signing.props.

That isn't going to workout. We need to find the path in sign.proj as each repo isn't going to have any better luck finding it. It gets put on the path in a VSDevCmd prompt based on my local prompt the sn tool lives in "C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.1 Tools" while not ideal to depend on that path we might be able to use it as a default. You might also have a look through https://docs.microsoft.com/en-us/dotnet/api/microsoft.build.utilities.toollocationhelper to see if there is a good API to call to get the path to the sdk.

[JohnTortugo]

That API is only for .NET Framework. I found a few alternatives but they don't work on .NET Core. I'll close this PR and resume the discussion on the issue: #1301

[ericstj]

I think we should have added a mapping for Sign.proj for the Open.snk given that Arcade is the one that's carrying it.