Fix build with Qt6 (#613)

find_package(QT ...) only finds out if Qt5 or Qt6 is available.
One needs to then to find_package(Qt5...) or find_package(Qt6...) as in
the Qt documentation:
https://doc.qt.io/qt-6/cmake-qt5-and-qt6-compatibility.html

Otherwise, one gets this error:
CMake Error: AUTOMOC for target linuxdeployqt: Could not find moc executable target Qt6::moc
CMake Generate step failed.  Build files cannot be regenerated correctly.

Co-authored-by: David Faure <[email protected]>

Author: dfaure-kdab

tools/linuxdeployqt/CMakeLists.txt

@@ -10,6 +10,7 @@ add_definitions("-DBUILD_DATE=\"${DATE}\"")
 add_definitions("-DBUILD_NUMBER=\"${BUILD_NUMBER}\"")
 
 find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core)
+find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core)
 
 # update excludelist
 message(STATUS "Updating excludelist...")