Add initial update-dependencies script.

This script can be used to automatically update dotnet/cli's
dependencies on other repos like CoreFX, NuGet, etc.

Currently the script supports updating the CoreFX dependencies.

scripts/update-dependencies/Program.cs

@@ -0,0 +1,25 @@
+// 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 Microsoft.DotNet.Cli.Build.Framework;
+
+namespace Microsoft.DotNet.Scripts
+{
+    public class Program
+    {
+        public static int Main(string[] args)
+        {
+            DebugHelper.HandleDebugSwitch(ref args);
+
+            return BuildSetup.Create(".NET CLI Dependency Updater")
+                .UseTargets(new[]
+                {
+                    new BuildTarget("Default", "Dependency Updater Goals", new [] { "UpdateFiles", "PushPR" }),
+                    new BuildTarget("UpdateFiles", "Dependency Updater Goals"),
+                    new BuildTarget("PushPR", "Dependency Updater Goals"),
+                })
+                .UseAllTargetsFromAssembly<Program>()
+                .Run(args);
+        }
+    }
+}