Build-Time Hello World Performance Test (#2681)

Hello world build performance benchmark.

test/Microsoft.DotNet.Tools.Tests.Utilities/NuGetConfig.cs

@@ -0,0 +1,27 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.IO;
+
+namespace Microsoft.DotNet.Tools.Test.Utilities
+{
+    public static class NuGetConfig
+    {
+        public static void Write(string directory)
+        {
+            var contents = @"<?xml version=""1.0"" encoding=""utf-8""?>
+<configuration>
+<packageSources>
+<!--To inherit the global NuGet package sources remove the <clear/> line below -->
+<clear />
+<add key=""dotnet-core"" value=""https://dotnet.myget.org/F/dotnet-core/api/v3/index.json"" />
+<add key=""api.nuget.org"" value=""https://api.nuget.org/v3/index.json"" />
+</packageSources>
+</configuration>";
+
+            var path = Path.Combine(directory, "NuGet.config");
+
+            File.WriteAllText(path, contents);
+        }
+    }
+}