Fix build with CMake 3.26:
https://github.com/fcitx/fcitx5-kkc/commit/85b56d6289550174b15f108e355f39d7083f8c5c

Index: gui/CMakeLists.txt
--- gui/CMakeLists.txt.orig
+++ gui/CMakeLists.txt
@@ -17,12 +17,11 @@ qt5_wrap_ui(KKC_CONFIG_SRCS dictwidget.ui adddictdialo
 add_library(fcitx5-kkc-config
   MODULE ${KKC_CONFIG_SRCS})
 
-add_definitions(-DQT_NO_KEYWORDS -std=c++11)
+add_definitions(-DQT_NO_KEYWORDS)
 
 target_include_directories(fcitx5-kkc-config PRIVATE ${PROJECT_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR})
 
 set_target_properties(fcitx5-kkc-config PROPERTIES
-                      LINK_FLAGS "-Wl,--no-undefined"
                       AUTOMOC TRUE
                       AUTOUIC TRUE
                       AUTOUIC_OPTIONS "-tr=fcitx::tr2fcitx;--include=fcitxqti18nhelper.h")