CMake: Move add_subdirectory(impl) calls for styles to the frontHEADdev

Otherwise in a static build on macOS we get the warnings below, which
happen when a target references a dependency that has not been created
yet.

CMake Warning at qtbase/cmake/QtFindPackageHelpers.cmake:551 (message):
  Could not find target Qt6::QuickControls2MacOSStyleImpl to query its
  package name.  Defaulting to package name
  Qt6QuickControls2MacOSStyleImpl.
  Consider re-arranging the project structure to ensure the target exists by
  this point.
Call Stack (most recent call first):
  cmake/QtFindPackageHelpers.cmake:601
   (qt_internal_get_package_name_of_target)
  cmake/QtTargetHelpers.cmake:240 (qt_register_target_dependencies)
  cmake/QtPluginHelpers.cmake:285 (qt_internal_extend_target)
  src/qml/Qt6QmlBuildInternals.cmake:216 (qt_internal_add_plugin)
  src/quickcontrols/macos/CMakeLists.txt:42
   (qt_internal_add_qml_module)

Pick-to: 6.7
Change-Id: I8759f21ee463765486908e49e996004f3b3e618c
Reviewed-by:  Alexey Edelev <alexey.edelev@qt.io>

0 files changed, 0 insertions, 0 deletions