Add diagnostic verbosity to all msbuild commands. Test output is going to be long.

Author: marcpopMSFT

build/RunTestsOnHelix.cmd

@@ -23,7 +23,6 @@ mkdir %TestExecutionDirectory%
 REM https://stackoverflow.com/a/7487697/294804
 robocopy %HELIX_CORRELATION_PAYLOAD%\t\TestExecutionDirectoryFiles %TestExecutionDirectory% /s /nfl /ndl /njh /njs /np
 
-set Verbosity=diagnostic
 set DOTNET_SDK_TEST_EXECUTION_DIRECTORY=%TestExecutionDirectory%
 set DOTNET_SDK_TEST_MSBUILDSDKRESOLVER_FOLDER=%HELIX_CORRELATION_PAYLOAD%\r
 set DOTNET_SDK_TEST_ASSETS_DIRECTORY=%TestExecutionDirectory%\TestAssets

test/Microsoft.NET.TestFramework/Commands/MSBuildCommand.cs

@@ -133,6 +133,8 @@ public override CommandResult Execute(IEnumerable<string> args)
                 args = new[] { "/restore" }.Concat(args);
             }
 
+            args = args.Concat(new[] { "-v:diag" });
+
             return base.Execute(args);
         }