CMake: link with Qt6 cmake targets

Using Qt6::DBus / Qt6::Core is more robust than relying on the
Qt6Core_LIBRARIES / Qt6DBus_LIBRARIES libraries.
It seems that not every Qt installation provides these variables. This
most notably fixes compilation against conan-provided Qt

Author: timblechmann

CMakeLists.txt

@@ -105,8 +105,7 @@ else()
 
   if(UNIX AND NOT APPLE AND NOT ANDROID AND NOT HAIKU AND NOT EMSCRIPTEN)
     find_package(Qt6 COMPONENTS DBus REQUIRED)
-    include_directories(${Qt6DBus_INCLUDE_DIRS})
-    set(QTDBUS_LIBRARIES ${Qt6DBus_LIBRARIES})
+    set(QTDBUS_LIBRARIES Qt6::DBus)
     macro(qt_add_dbus_interface)
       qt6_add_dbus_interface(${ARGN})
     endmacro()
@@ -126,7 +125,7 @@ else()
     qt6_wrap_cpp(${ARGN})
   endmacro()
 
-  set(QTCORE_LIBRARIES ${Qt6Core_LIBRARIES})
+  set(QTCORE_LIBRARIES Qt6::Core)
 endif()
 
 set(QTKEYCHAIN_TARGET_NAME qt${QTKEYCHAIN_VERSION_INFIX}keychain)