Fix CMake FindQt.cmake to detect Qt installation path properly

(find_package):
[cmake]   Could not find a package configuration file provided by "QT" with any of
[cmake]   the following names:
[cmake]
[cmake]     Qt6Config.cmake
[cmake]     qt6-config.cmake
[cmake]     Qt5Config.cmake
[cmake]     qt5-config.cmake
[cmake]
[cmake]   Add the installation prefix of "QT" to CMAKE_PREFIX_PATH or set "QT_DIR" to
[cmake]   a directory containing one of the above files.  If "QT" provides a separate
[cmake]   development package or SDK, be sure it has been installed.