dotnet build fails with xmlDoc = true and spaces in the path.

Need to quote the xmlDoc argument to the csc compiler.

Fix #2600

TestAssets/TestProjects/TestLibrary With Spaces/Helper.cs

@@ -0,0 +1,24 @@
+// 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;
+
+namespace TestLibrary
+{
+    public static class Helper
+    {
+        /// <summary>
+        /// Gets the message from the helper. This comment is here to help test XML documentation file generation, please do not remove it.
+        /// </summary>
+        /// <returns>A message</returns>
+        public static string GetMessage()
+        {
+            return "This string came from the test library!";
+        }
+
+        public static void SayHi()
+        {
+            Console.WriteLine("Hello there!");
+        }
+    }
+}

TestAssets/TestProjects/TestLibrary With Spaces/project.json

@@ -0,0 +1,12 @@
+{
+  "version": "1.0.0-*",
+  "compilationOptions": {
+    "xmlDoc": true
+  },
+  "dependencies": {
+    "NETStandard.Library": "1.5.0-rc2-24027"
+  },
+  "frameworks": {
+    "netstandard1.3": {}
+  }
+}

src/dotnet/commands/dotnet-compile-csc/Program.cs

@@ -189,7 +189,7 @@ namespace Microsoft.DotNet.Tools.Compiler.Csc
 
             if (options.GenerateXmlDocumentation == true)
             {
-                commonArgs.Add($"-doc:{Path.ChangeExtension(outputName, "xml")}");
+                commonArgs.Add($"-doc:\"{Path.ChangeExtension(outputName, "xml")}\"");
             }
 
             if (options.EmitEntryPoint != true)

test/Microsoft.DotNet.Tools.Tests.Utilities/Commands/TestCommand.cs

@@ -14,7 +14,7 @@ namespace Microsoft.DotNet.Tools.Test.Utilities
     public class TestCommand
     {
         protected string _command;
-        
+
         private string _baseDirectory;
 
         public string WorkingDirectory { get; set; }
@@ -33,6 +33,12 @@ namespace Microsoft.DotNet.Tools.Test.Utilities
 #endif 
         }
 
+        public TestCommand WithWorkingDirectory(string workingDirectory)
+        {
+            WorkingDirectory = workingDirectory;
+            return this;
+        }
+
         public virtual CommandResult Execute(string args = "")
         {
             var commandPath = _command;

test/dotnet-build.Tests/GivenDotnetBuildBuildsProjects.cs

@@ -42,5 +42,19 @@ namespace Microsoft.DotNet.Tools.Builder.Tests
                 .Should()
                 .Pass();
         }
+
+        [Fact]
+        public void It_builds_projects_with_spaces_in_the_path()
+        {
+            var testInstance = TestAssetsManager
+                .CreateTestInstance("TestLibrary With Spaces")
+                .WithLockFiles();
+
+            new BuildCommand("")
+                .WithWorkingDirectory(testInstance.TestRoot)
+                .ExecuteWithCapturedOutput()
+                .Should()
+                .Pass();
+        }
     }
 }