qt_add_translations: CFBundleLocalizations might not be added to Info.plist

https://codereview.qt-project.org/c/qt/qtbase/+/473581 added functionality to add known translations to CFBundleLocalizations in Info.plist. It is supposed to work like this:

• qt_add_translations(foo TS_FILES ...) reads the languages from the .ts files
• qt_add_translations sets the property _qt_apple_supported_languages on foo
• foo's target finalizer reads _qt_apple_supported_languages and adds the information to the Info.plist content

This is broken in the following project setup:

# CMakeLists.txt
cmake_minimum_required(VERSION 3.16)
project(throwaway)
set(CMAKE_CXX_STANDARD 20)
find_package(Qt6 COMPONENTS Core LinguistTools)
qt_standard_project_setup()
add_subdirectory(subdir)
qt_add_translations(foo TS_FILES foo_de.ts)

# subdir/CMakeLists.txt
qt_add_executable(foo
    main.cpp)

foo's target finalizer runs before qt_add_translations sets the property, and CFBundleLocalizations is not added to Info.plist.