title: What is the purpose of msbuild's GenerateRuntimeConfigurationFiles?
body: <p>I upgraded a netcore1.1 project to the new VS2017/csproj.</p>
  
  <p>In my test projects only, it added:</p>
  
  <pre><code>&lt;PropertyGroup&gt;
    &lt;GenerateRuntimeConfigurationFiles&gt;true&lt;/GenerateRuntimeConfigurationFiles&gt;
  &lt;/PropertyGroup&gt;
  </code></pre>
  
  <p>I did <a href="https://github.com/dotnet/sdk/blob/master/src/Tasks/Microsoft.NET.Build.Tasks/GenerateRuntimeConfigurationFiles.cs" rel="noreferrer">some digging</a> to discover that it generates these files in the bin directory:</p>
  
  <ul>
  <li><code>ProjectName.Tests.runtimeconfig.json</code></li>
  <li><code>ProjectName.Tests.runtimeconfig.dev.json</code></li>
  </ul>
  
  <p>What is this setting and these files, and why do I need them?</p>
  
  <p>Why were they only generated for my test projects?</p>