Tell MSVC that our source code is UTF-8 encoded

Without making this explicit MSVC gets creative on its own, resulting in
code with UTF-8 literals not building, or UTF-8 literals being wrongly
decoded.

CMakeLists.txt

@@ -10,6 +10,9 @@ find_package(ECM ${KF5_MIN_VERSION} REQUIRED NO_MODULE)
 set(CMAKE_MODULE_PATH ${ECM_MODULE_PATH} ${CMAKE_SOURCE_DIR}/cmake)
 
 include(KDEFrameworkCompilerSettings NO_POLICY_SCOPE)
+if (MSVC)
+    add_compile_options(/source-charset:utf-8 /execution-charset:utf-8)
+endif()
 include(ECMAddTests)
 include(ECMGenerateHeaders)
 include(ECMQtDeclareLoggingCategory)