FindProtobuf: C++11 support is required since version 3.6.0

Modules/FindProtobuf.cmake

@@ -521,6 +521,11 @@ if(Protobuf_INCLUDE_DIR)
             set_target_properties(protobuf::libprotobuf PROPERTIES
               IMPORTED_LOCATION_DEBUG "${Protobuf_LIBRARY_DEBUG}")
           endif()
+          if (Protobuf_VERSION VERSION_GREATER_EQUAL "3.6")
+            set_property(TARGET protobuf::libprotobuf APPEND PROPERTY
+              INTERFACE_COMPILE_FEATURES cxx_std_11
+            )
+          endif()
           if(UNIX AND TARGET Threads::Threads)
             set_property(TARGET protobuf::libprotobuf APPEND PROPERTY
                 INTERFACE_LINK_LIBRARIES Threads::Threads)