CMake couldn't find "FindWMF.cmake" in top-level builds

This bug only happens in top-level builds.

Configure a top-level build on Windows:

cmake D:/Qt/src/qt6 -DBUILD_qtwebengine=OFF -DBUILD_qtwebview=OFF -GNinja -DCMAKE_BUILD_TYPE=Release -Wno-dev

You could see a lot of warnings when configuring qtsensors:

Configuring 'qtsensors'
CMake Warning at D:/tools/cmake-3.21.1-windows-x86_64/share/cmake-3.21/Modules/CMakeFindDependencyMacro.cmake:47 (find_package):
By not providing "FindWMF.cmake" in CMAKE_MODULE_PATH this project has
asked CMake to find a package configuration file provided by "WMF", but
CMake did not find one.

Could not find a package configuration file provided by "WMF" with any of
the following names:

WMFConfig.cmake
wmf-config.cmake

Add the installation prefix of "WMF" to CMAKE_PREFIX_PATH or set "WMF_DIR"
to a directory containing one of the above files. If "WMF" provides a
separate development package or SDK, be sure it has been installed.
Call Stack (most recent call first):
D:/Qt/build-dev-vs2019_64-shared/qtbase/lib/cmake/Qt6Multimedia/Qt6MultimediaDependencies.cmake:45 (find_dependency)
D:/Qt/build-dev-vs2019_64-shared/qtbase/lib/cmake/Qt6Multimedia/Qt6MultimediaConfig.cmake:40 (include)
D:/Qt/build-dev-vs2019_64-shared/qtbase/lib/cmake/Qt6/Qt6Config.cmake:127 (find_package)
qtsensors/CMakeLists.txt:14 (find_package)

CMake Warning at D:/Qt/build-dev-vs2019_64-shared/qtbase/lib/cmake/Qt6/Qt6Config.cmake:127 (find_package):
Found package configuration file:

D:/Qt/build-dev-vs2019_64-shared/qtbase/lib/cmake/Qt6Multimedia/Qt6MultimediaConfig.cmake

but it set Qt6Multimedia_FOUND to FALSE so package "Qt6Multimedia" is
considered to be NOT FOUND. Reason given by package:

Qt6Multimedia could not be found because dependency WMF could not be found.

Call Stack (most recent call first):
qtsensors/CMakeLists.txt:14 (find_package)

CMake Warning at D:/Qt/build-dev-vs2019_64-shared/qtbase/lib/cmake/Qt6/Qt6Config.cmake:166 (message):
Failed to find Qt component "Multimedia".

Expected Config file at
"D:/Qt/build-dev-vs2019_64-shared/qtbase/lib/cmake/Qt6Multimedia/Qt6MultimediaConfig.cmake"
exists

Call Stack (most recent call first):
qtsensors/CMakeLists.txt:14 (find_package)