Missing default CFBundleIdentifier in CMake generated projects

With qmake there's no need to set an explicit bundle identifier, regardless of which generator is used (makefile, Xcode). If one is not set, we generate a placeholder based on the QMAKE_TARGET_BUNDLE_PREFIX (which we read from the Xcode settings if not set), and the bundle name (QMAKE_BUNDLE).

With CMake we only do this for Xcode projects (see _qt_internal_set_xcode_bundle_identifier), resulting in an empty identifier in ninja-geneated projects.

This has subtle effects on e.g. the system permission machinery, since it fails to store permissions, and might have other subtle effects that are hard to diagnose.