KDE4_INCLUDES also contains Qt includes required by KDE.
See FindKDE4Internal.cmake for more details.

--- kdialogd4/CMakeLists.txt
+++ kdialogd4/CMakeLists.txt
@@ -1,4 +1,4 @@
-include_directories (${CMAKE_SOURCE_DIR} ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_SOURCE_DIR}/common ${CMAKE_BINARY_DIR} ${KDE4_INCLUDE_DIR} ${QT_INCLUDE_DIR})
+include_directories (${CMAKE_SOURCE_DIR} ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_SOURCE_DIR}/common ${CMAKE_BINARY_DIR} ${KDE4_INCLUDES} ${QT_INCLUDE_DIR})
 set(kdialogd4_bin_SRCS kdialogd.cpp)
 kde4_add_executable(kdialogd4_bin ${kdialogd4_bin_SRCS})
 set_target_properties(kdialogd4_bin PROPERTIES OUTPUT_NAME kdialogd4)