CMake: repair KDE Frameworks 6 dependencies

Be a little more chatty and look for the correct KDE Frameworks
for consumers of Calamares (e.g. calamares-extensions).

CalamaresConfig.cmake.in

@@ -49,8 +49,12 @@ endmacro()
 set(Calamares_WITH_QT6 @WITH_QT6@)
 if(Calamares_WITH_QT6)
     set(qtname "Qt6")
+    set(kfname "kf6")
+    message(STATUS "Calamares was built with Qt6 and KDE Frameworks 6")
 else()
     set(qtname "Qt5")
+    set(kfname "kf5")
+    message(STATUS "Calamares was built with Qt5 and KDE Frameworks 5 (legacy)")
 endif()
 
 # Qt infrastructure for translations is required
@@ -59,14 +63,14 @@ accumulate_deps(qt_required Calamares::calamares ${qtname}::)
 accumulate_deps(qt_required Calamares::calamaresui ${qtname}::)
 find_package(${qtname} CONFIG REQUIRED ${qt_required})
 
-set(kf5_required "")
-accumulate_deps(kf5_required Calamares::calamares ${kfname}::)
-accumulate_deps(kf5_required Calamares::calamaresui ${kfname}::)
-if(kf5_required)
+set(kf_required "")
+accumulate_deps(kf_required Calamares::calamares ${kfname}::)
+accumulate_deps(kf_required Calamares::calamaresui ${kfname}::)
+if(kf_required)
     find_package(ECM ${ECM_VERSION} NO_MODULE)
     if( ECM_FOUND )
         list(INSERT CMAKE_MODULE_PATH 0 ${ECM_MODULE_PATH})
-        find_package(${kfname} REQUIRED COMPONENTS ${kf5_required})
+        find_package(${kfname} REQUIRED COMPONENTS ${kf_required})
     endif()
 endif()