Remove old stuff about updated files

This dates from the time we were using timestamps for incremental
compilation.

src/action.ml

@@ -543,17 +543,6 @@ let fold_one_step t ~init:acc ~f =
 
 include Make_mapper(Ast)(Ast)
 
-let updated_files =
-  let rec loop acc t =
-    let acc =
-      match t with
-      | Write_file (fn, _) -> Path.Set.add fn acc
-      | _ -> acc
-    in
-    fold_one_step t ~init:acc ~f:loop
-  in
-  fun t -> loop Path.Set.empty t
-
 let chdirs =
   let rec loop acc t =
     let acc =

src/action.mli

@@ -44,9 +44,6 @@ include Action_intf.Helpers
 val t : t Sexp.Of_sexp.t
 val sexp_of_t : t Sexp.To_sexp.t
 
-(** Return the list of files under an [Update_file] *)
-val updated_files : t -> Path.Set.t
-
 (** Return the list of directories the action chdirs to *)
 val chdirs : t -> Path.Set.t
 

src/build_system.ml

@@ -672,13 +672,8 @@ let rec compile_rule t ?(copy_source=false) pre_rule =
       List.exists targets_as_list ~f:Path.is_alias_stamp_file
     in
     if deps_or_rule_changed || targets_missing || force then (
-      (* Do not remove files that are just updated, otherwise this would break incremental
-         compilation *)
-      let targets_to_remove =
-        Pset.diff targets (Action.updated_files action)
-      in
-      Pset.iter targets_to_remove ~f:Path.unlink_no_err;
-      pending_targets := Pset.union targets_to_remove !pending_targets;
+      List.iter targets_as_list ~f:Path.unlink_no_err;
+      pending_targets := Pset.union targets !pending_targets;
       let action =
         match sandbox_dir with
         | Some sandbox_dir ->
@@ -703,7 +698,7 @@ let rec compile_rule t ?(copy_source=false) pre_rule =
         Action.exec ?context ~targets action) >>| fun () ->
       Option.iter sandbox_dir ~f:Path.rm_rf;
       (* All went well, these targets are no longer pending *)
-      pending_targets := Pset.diff !pending_targets targets_to_remove;
+      pending_targets := Pset.diff !pending_targets targets;
       clear_targets_digests_after_rule_execution targets_as_list;
       match mode with
       | Standard | Fallback | Not_a_rule_stanza | Ignore_source_files -> ()