I believe I resolved this (for me at least):
I went through the project in Xcode and updated the files listed under extensions/CocoStudio to match what actually exists under the extensions/CocoStudio SDK folder. It looks like CocoStudio was significantly updated between release 2.2.1 and 2.2.2 but not all the changes made it in to the Mac project template.
After this I was able to successfully build and run the Mac project.
(I didn't mention before, but the Mac Xcode project I was using was created using tools/project-creator/create_project.py script.)
Specifically: under extensions/CocoStudio
removed project references to:
GUI/BaseClasses/UIRootWidget.cpp GUI/BaseClasses/UIRootWidget.h GUI/UIWidgets/ScrollWidget/UIListViewEx.h GUI/UIWidgets/ScrollWidget/UIListViewEx.cpp GUI/UIWidgets/UISwitch.cpp GUI/UIWidgets/UISwitch.hadded project references to: