sdktool: Don't rely on FindQt5.cmake

Use the normal CMake mechanism for finding either Qt 5 or Qt 6, instead
of relying of the mapping from Qt 6 to Qt 5 that is done via the custom
FindQt5.cmake.

Change-Id: Ia9a17d82edfb2f27e10918f05ce8a0d34d9bb5f8
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/tools/sdktool/CMakeLists.txt

@@ -16,15 +16,19 @@ if (NOT QT_CREATOR_API_DEFINED)
   set(DESTINATION DESTINATION .)
   include(QtCreatorIDEBranding)
   include(QtCreatorAPI)
+
+  find_package(QT NAMES Qt6 Qt5
+    COMPONENTS Core
+    REQUIRED
+  )
+  find_package(Qt${QT_VERSION_MAJOR}
+    COMPONENTS Core
+    REQUIRED
+  )
 endif()
 
 configure_file(../../app/app_version.h.cmakein app/app_version.h ESCAPE_QUOTES)
 
-find_package(Qt5
-  COMPONENTS Core
-  REQUIRED
-)
-
 if (APPLE)
   find_library(FWFoundation Foundation)
 endif()