Use Env.t over string array in another place

bin/main.ml

@@ -49,6 +49,7 @@ let set_common c ~targets =
       ]
 
 let restore_cwd_and_execve common prog argv env =
+  let env = Env.to_unix env in
   let prog =
     if Filename.is_relative prog then
       Filename.concat common.root prog

src/context.ml

@@ -433,7 +433,7 @@ let env_for_exec t =
         (Config.local_install_man_dir ~context:t.name)
     ]
   in
-  Env.to_unix (Env.extend t.env ~vars:(Env.Map.of_list_exn vars))
+  Env.extend t.env ~vars:(Env.Map.of_list_exn vars)
 
 let compiler t (mode : Mode.t) =
   match mode with

src/context.mli

@@ -130,7 +130,7 @@ val opam_config_var : t -> string -> string option Fiber.t
 val install_prefix : t -> Path.t Fiber.t
 val install_ocaml_libdir : t -> Path.t option Fiber.t
 
-val env_for_exec : t -> string array
+val env_for_exec : t -> Env.t
 
 (** Return the compiler needed for this compilation mode *)
 val compiler : t -> Mode.t -> Path.t option

src/env.ml

@@ -69,6 +69,9 @@ let add t ~var ~value =
 let extend t ~vars =
   make (Map.union t.vars vars ~f:(fun _ _ v -> Some v))
 
+let extend_env x y =
+  extend x ~vars:y.vars
+
 let sexp_of_t t =
   let open Sexp.To_sexp in
   (list (pair string string)) (Map.to_list t.vars)

src/env.mli

@@ -17,6 +17,8 @@ val get : t -> Var.t -> string option
 
 val extend : t -> vars:string Map.t -> t
 
+val extend_env : t -> t -> t
+
 val add : t -> var:Var.t -> value:string -> t
 
 val diff : t -> t -> t