Require C++17

Like we do for other Plasma repos already

CMakeLists.txt

@@ -6,6 +6,9 @@ set(PROJECT_VERSION "5.20.80")
 set(QT_MIN_VERSION "5.15.0")
 set(KF5_MIN_VERSION "5.74")
 
+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})