[mtouch tests] Format output spew better to make it easier to parse by mere humans.

tests/common/ExecutionHelper.cs

@@ -60,7 +60,7 @@ namespace Xamarin.Tests
 
 			if (rv != 0) {
 				if (output.Length > 0)
-					Console.WriteLine (output);
+					Console.WriteLine ("\t" + output.ToString ().Replace ("\n", "\n\t"));
 			}
 
 			ParseMessages ();