Make it compiles against qt6

CMakeLists.txt

@@ -7,7 +7,7 @@ cmake_minimum_required (VERSION 3.16 FATAL_ERROR)
 project(ktimer VERSION ${RELEASE_SERVICE_VERSION})
 
 set (QT_MIN_VERSION "5.15.0")
-set(KF5_MIN_VERSION "5.85.0")
+set(KF5_MIN_VERSION "5.89.0")
 
 find_package (ECM ${KF5_MIN_VERSION} REQUIRED NO_MODULE)
 set (CMAKE_MODULE_PATH ${ECM_MODULE_PATH})
@@ -19,10 +19,13 @@ include(KDECompilerSettings NO_POLICY_SCOPE)
 include(ECMInstallIcons)
 include(ECMAddAppIcon)
 
-find_package (Qt5 ${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS
+find_package (Qt${QT_MAJOR_VERSION} ${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS
     Core
     Widgets
 )
+if (QT_MAJOR_VERSION STREQUAL "6")
+    find_package(Qt6Core5Compat)
+endif()
 
 find_package(KF5 ${KF5_MIN_VERSION} REQUIRED COMPONENTS
     I18n