title: C# 8 features in .NET Framework 4.7.2
body: <p>In a c# project targeting .NET Framework 4.7.2 I made a local function static because Visual Studio (16.3.3) suggested it. Everything compiled and worked fine. But when I pushed this on my CI build server with the Visual Studio Build Tools (16.3.3) installed, it complained:</p>
  
  <blockquote>
    <p>error CS8652: The feature 'static local functions' is currently in Preview and <em>unsupported</em>. To use Preview features, use the 'preview' language version.</p>
  </blockquote>
  
  <p>What I could figure out is that static local functions are a C# 8 feature and C# 8 is not available for projects targeting .NET Framework 4.7.2. So why did it work on the first place and what can I do to make it compile on the build server?</p>