Require xkbcommon 0.4.1

That's the version required in Qt 5.3 and causing issues if there's a
mismatch in versions.

CCBUG: 333459

CMakeLists.txt

@@ -118,7 +118,7 @@ set_package_properties(Wayland PROPERTIES
 add_feature_info("Wayland-Client" Wayland_Client_FOUND "Required for building the Wayland backend in KWin")
 add_feature_info("Wayland-EGL" Wayland_Egl_FOUND "Required for building the Wayland EGL compositing backend in KWin")
 
-find_package(XKB)
+find_package(XKB 0.4.1)
 set_package_properties(XKB PROPERTIES
                        TYPE OPTIONAL
                        PURPOSE "Required for building KWin with Wayland support"

cmake/modules/FindXKB.cmake

@@ -46,6 +46,7 @@ if(NOT WIN32)
 
     set(XKB_LIBRARIES ${XKB_LIBRARY})
     set(XKB_INCLUDE_DIRS ${XKB_INCLUDE_DIR})
+    set(XKB_VERSION ${PKG_XKB_VERSION})
 
     include(FindPackageHandleStandardArgs)
     find_package_handle_standard_args(XKB
@@ -54,6 +55,8 @@ if(NOT WIN32)
         REQUIRED_VARS
             XKB_LIBRARY
             XKB_INCLUDE_DIR
+        VERSION_VAR
+            XKB_VERSION
     )
 
     if(XKB_FOUND AND NOT TARGET XKB::XKB)