IMO, it could be a Recommends or Suggests, as long as the library is clear about what the user should do if the library is needed but not installed. I.e. a stderr warning like "libpcsc not found" would work.
IMO, it could be a Recommends or Suggests, as long as the library is clear about what the user should do if the library is needed but not installed. I.e. a stderr warning like "libpcsc not found" would work.