message: Fix install with external protobuf
diff: @@ -44,8 +44,10 @@ else()
  if(Protobuf_FOUND)
  if(TARGET protobuf::libprotobuf)
  - add_library(libprotobuf INTERFACE)
  - target_link_libraries(libprotobuf INTERFACE protobuf::libprotobuf)
  + add_library(libprotobuf INTERFACE IMPORTED)
  + set_target_properties(libprotobuf PROPERTIES
  + INTERFACE_LINK_LIBRARIES protobuf::libprotobuf
  + )
  else()
  add_library(libprotobuf UNKNOWN IMPORTED)
  set_target_properties(libprotobuf PROPERTIES
  