Set CXX standard for crossbuilding utility

(cherry picked from commit 484d2da0465f531158e217def769a3aef80039c6)

src/wayland/tools/CMakeLists.txt

@@ -3,6 +3,7 @@
 if (${CMAKE_CURRENT_SOURCE_DIR} STREQUAL ${CMAKE_SOURCE_DIR})
     cmake_minimum_required(VERSION 3.16)
     project(qtwaylandscanner_kde CXX)
+    set(CMAKE_CXX_STANDARD 20)
     find_package(Qt5 5.15.0 CONFIG REQUIRED Core)
     find_package(ECM ${KF5_MIN_VERSION} NO_MODULE REQUIRED)
     set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH})

src/wayland/tools/qtwaylandscanner.cpp

@@ -42,6 +42,7 @@
 #include <QXmlStreamReader>
 
 #include <vector>
+#include <utility>
 
 class Scanner
 {