GetUnityMainTargetGuid returns null when building Xcode project

Hi,

I'm having this issue recently after upgrading to 2020.1 from 2019.4

GetUnityMainTargetGuid() returns null, but I can see that the PBXProject object has the correct guid if I dig down the data in the debugger.

Is there a different way to get the GUID?

Using this code with Unity 2020.1.4f1:

Code (CSharp):

1. public static void OnPostProcessBuild(BuildTarget buildTarget, string pathToBuiltProject)
2. {
3.     var project = new PBXProject();
4.     var projectFile = Path.Combine(pathToBuiltProject, "project.pbxproj");
5.     project.ReadFromFile(projectFile);
6.  
7.     var targetGUID = project.GetUnityMainTargetGuid(); // This is null
8. }

Thanks!