-Wno-inconsistent-missing-override on Clang

This is a totally stupid warning for an older code base such as KWin. It
generates hundreds of warnings as on legacy code no method uses override.
The output is totally spammed, so it's better to disable it.

This will hopefully also prevent that someone tries to fix it again by
changing all of KWin - which we don't want.

CMakeLists.txt

@@ -51,6 +51,10 @@ add_definitions(-DQT_DISABLE_DEPRECATED_BEFORE=0 -DQT_USE_QSTRINGBUILDER)
 set(CMAKE_CXX_STANDARD 14)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-inconsistent-missing-override")
+endif()
+
 find_package(Qt5Multimedia QUIET)
 set_package_properties(Qt5Multimedia PROPERTIES
          PURPOSE "Runtime-only dependency for effect video playback"