In case CMAKE_XCODE_GENERATE_TOP_LEVEL_PROJECT_ONLY has been enabled
generate only the root-level ZERO_CHECK target so targets in
subdirectories pick up the root generator target of ZERO_CHECK.

For the case that CMAKE_XCODE_GENERATE_TOP_LEVEL_PROJECT_ONLY is not
enabled more investigation and a proper and final fix is still needed.

Issue: 14297