When creating custom menus priority attribute does not update correctly until the project is restarted. Reimport or a refresh of the code does not seem to work either.

Steps to reproduce
- Open the attached project in Unity 2019.3.0b3
- Open the CreateBuild script in Visual Studio Code or Rider.
- Edit the priority of MenuItem("Build/Build All/Standalone 64-bit") to be 21. [MenuItem("Build/Build All/Standalone 64-bit", false, 21)]
- Save and go back to the editor
- Unity's top menu bar should have a Build option
- Select this option
Notice issue >> Build All should be at the bottom of the menu with a divider. But it's still at it's previous position of 0.

Tested not working
macOS 2019.3.0b1
Linux 2019.3.0b3
Linux 2017.4.32f1