Require C++17

Like we do for other Plasma stuff

CMakeLists.txt

@@ -7,6 +7,9 @@ set(PROJECT_VERSION_MAJOR 5)
 set(QT_MIN_VERSION "5.15.0")
 set(KF5_MIN_VERSION "5.78")
 
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
 find_package(ECM ${KF5_MIN_VERSION} REQUIRED NO_MODULE)
 set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH}  ${CMAKE_CURRENT_SOURCE_DIR}/cmake)