The Mobile Notification package executes a post-build Editor script that changes the Project file (iOSNotificationPostProcess). This post-process script only executes when PLATFORM_IOS is defined. When using the BuildPipeline.BuildPlayer from another Platform, this is not executed and leaves the Project unable to build. When building with Xcode, Customer gets "Undefined symbols" Error because the Notification Framework was not added to the Project

To reproduce:

1. Download attached "NotificationsCrossBuild.zip" project and open in Unity
2. Open Build Settings and change Target Platform to Mac OS X
3. Press Tests > Build
4. When Xcode project is built deploy it to the iOS device

Expected results: Xcode successfully deploys Project to the Device
Actual results: Project deployment fails and Xcode throws 8 Errors about Undefined symbols

Notes:
- This issue seems to be related only with iOS
- Cannot check on other Players because this Project is built specifically for iOS
- If Target Platform is set to iOS, then everything works as Expected
- Cannot check on preview.4 - 1.0.0 and lower Package version, because Project becomes corrupted

Reproduced on Package preview.5 - 1.0.0 and preview.2 - 1.0.4

Reproduced on Unity 2019.2.7f2, 2019.3.0b5 and 2020.1.0a5