Determine how to do authenticode verification with SignCheck on .NET Core

[ellahathaway]

Authenticode verification is currently unavailable on .NET Core, which prevents us from verifying multiple file types (e.g., .dll and .ps1) on macOS and Linux. We need to devise a workaround for this limitation.

One potential solution is to use osslsigncode. Another option is to skip checking these files on .NET Core, publish the skipped files, and then process them in a subsequent run of SignCheck using .NET Framework.