let print_build_status f =
    function
    | Bbuilt -> pp_print_string f "Bbuilt"
    | Bnot_built_yet -> pp_print_string f "Bnot_built_yet"
    | Bcannot_be_built -> pp_print_string f "Bcannot_be_built"
    | Bsuspension(cmd, _) ->
        fprintf f "@[<2>Bsuspension(%a,@ (<fun> : unit -> unit))@]" Command.print cmd