Module Stdune.Spawn

Subset of https://github.com/janestreet/spawn/blob/master/src/spawn.mli

module Env : sig ... end
val spawn : ?env:Env.t -> prog:string -> argv:string list -> ?stdin:Unix.file_descr -> ?stdout:Unix.file_descr -> ?stderr:Unix.file_descr -> unit -> Pid.t