[WiP] enable /m by default (#4543)

* MSBuild integration project + refactoring

* Feature Complete

* Change default target to an existing one

test/msbuild.IntegrationTests/GivenDotnetInvokesMSBuild.cs

@@ -0,0 +1,35 @@
+// 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.Tools.Test.Utilities;
+using Xunit;
+using System;
+using System.IO;
+using FluentAssertions;
+using Microsoft.DotNet.TestFramework;
+using Microsoft.DotNet.Cli.Utils;
+
+namespace Microsoft.DotNet.Cli.MSBuild.IntegrationTests
+{
+    public class GivenDotnetInvokesMSBuild : TestBase
+    {
+        [Theory]
+        [InlineData("build")]
+        [InlineData("clean")]
+        [InlineData("msbuild")]
+        [InlineData("pack")]
+        [InlineData("publish")]
+        [InlineData("test")]
+        public void When_dotnet_command_invokes_msbuild_Then_env_vars_and_m_are_passed(string command)
+        {
+            var testInstance = TestAssets.Get("MSBuildIntegration")
+                .CreateInstance(identifier: command)
+                .WithSourceFiles();
+
+            new DotnetCommand()
+                .WithWorkingDirectory(testInstance.Root)
+                .Execute(command)
+                .Should().Pass();
+        }
+    }
+}

test/msbuild.IntegrationTests/project.json

@@ -0,0 +1,23 @@
+{
+  "version": "1.0.0-*",
+  "dependencies": {
+    "Microsoft.NETCore.App": {
+      "type": "platform",
+      "version": "1.0.0"
+    },
+    "Microsoft.DotNet.Tools.Tests.Utilities": {
+      "target": "project"
+    },
+    "xunit": "2.2.0-beta3-build3330",
+    "dotnet-test-xunit": "1.0.0-rc2-330423-54"
+  },
+  "frameworks": {
+    "netcoreapp1.0": {
+      "imports": [
+        "dotnet5.4",
+        "portable-net451+win8"
+      ]
+    }
+  },
+  "testRunner": "xunit"
+}