Fix warnings

src/BenchmarkDotNet.Toolchains.Roslyn/Toolchains/RoslynToolchain.cs

@@ -2,6 +2,9 @@
 
 namespace BenchmarkDotNet.Toolchains
 {
+    /// <summary>
+    /// Build a benchmark program with the Roslyn compiler.
+    /// </summary>
     public class RoslynToolchain : Toolchain
     {
         internal RoslynToolchain() : base("Classic", new RoslynGenerator(), new RoslynBuilder(), new Executor())

tests/BenchmarkDotNet.Tests/CodeGeneratorTests.cs

@@ -26,6 +26,8 @@ namespace BenchmarkDotNet.Tests
             Assert.Throws<NotSupportedException>(() => CodeGenerator.Generate(benchmark));
         }
 
+
+        #pragma warning disable CS1998
         [Benchmark]
         public async void AsyncVoidMethod() { }
     }