Add DotnetRunner.

src/WixBuildTools.TestSupport/DotnetRunner.cs

@@ -0,0 +1,57 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixBuildTools.TestSupport
+{
+    using System;
+    using System.Collections.Generic;
+    using System.IO;
+
+    public class DotnetRunner : ExternalExecutable
+    {
+        private static readonly object InitLock = new object();
+        private static bool Initialized;
+        private static DotnetRunner Instance;
+
+        public static ExternalExecutableResult Execute(string command, string[] arguments = null) =>
+            InitAndExecute(command, arguments);
+
+        private static ExternalExecutableResult InitAndExecute(string command, string[] arguments)
+        {
+            lock (InitLock)
+            {
+                if (!Initialized)
+                {
+                    Initialized = true;
+                    var dotnetPath = Environment.GetEnvironmentVariable("DOTNET_HOST_PATH");
+                    if (String.IsNullOrEmpty(dotnetPath) || !File.Exists(dotnetPath))
+                    {
+                        dotnetPath = "dotnet";
+                    }
+
+                    Instance = new DotnetRunner(dotnetPath);
+                }
+            }
+
+            return Instance.ExecuteCore(command, arguments);
+        }
+
+        private DotnetRunner(string exePath) : base(exePath) { }
+
+        private ExternalExecutableResult ExecuteCore(string command, string[] arguments)
+        {
+            var total = new List<string>
+            {
+                command,
+            };
+
+            if (arguments != null)
+            {
+                total.AddRange(arguments);
+            }
+
+            var args = CombineArguments(total);
+            var mergeErrorIntoOutput = true;
+            return this.Run(args, mergeErrorIntoOutput);
+        }
+    }
+}