Display .NET SDK version

[Jericho]

It would be great for Cake.Recipe to display info about the version of .NET SDK being used.

Currently, the only clue we have is the MSBuild version like in this example:

========================================
DotNetCore-Build
========================================
Building Source/Cake.Email.Common.sln
MSBuild version 17.8.3+195e7f5a3 for .NET

and then we have to figure out what version of .NET SDK corresponds to 17.8.3 by looking it up here.

What I would like to see, is the result of the dotnet --version command. Bonus points if we get additional info similar to what we get when running the dotnet --info command.

[Jericho]

For the time being, I added the following in my appveyor.yml:

before_build:
  - dotnet --info

This gives me the info I want when my build is running on AppVeyor but I still think it would be beneficial to add this to Cake.Recipe.