From b5f0a3513c3706e843eedfd91f07f38017f19f1e Mon Sep 17 00:00:00 2001
From: David Allsopp <david.allsopp@metastack.com>
Date: Wed, 8 Nov 2023 10:26:20 +0000
Subject: [PATCH] Fix 4.08/4.09 build

---
 src/core/opamCompat.ml  | 12 ++++++++++++
 src/core/opamCompat.mli |  5 +++++
 2 files changed, 17 insertions(+)

diff --git a/src/core/opamCompat.ml b/src/core/opamCompat.ml
index 216376563aa..773fee94590 100644
--- a/src/core/opamCompat.ml
+++ b/src/core/opamCompat.ml
@@ -147,3 +147,15 @@ Quoting commands for execution by cmd.exe is difficult.
 
   include Stdlib.Filename
 end
+
+module List = struct
+  [@@@warning "-32"]
+
+  let concat_map f l =
+    let rec aux f acc = function
+      | [] -> List.rev acc
+      | x :: l ->
+         let xs = f x in
+         aux f (List.rev_append xs acc) l
+    in aux f [] l
+end
diff --git a/src/core/opamCompat.mli b/src/core/opamCompat.mli
index 9596aedbb82..9846b4b7f14 100644
--- a/src/core/opamCompat.mli
+++ b/src/core/opamCompat.mli
@@ -38,3 +38,8 @@ module Filename: sig
     string -> ?stdin:string -> ?stdout:string -> ?stderr:string
     -> string list -> string
 end
+
+module List : sig
+  (* NOTE: OCaml >= 4.10 *)
+  val concat_map : ('a -> 'b list) -> 'a list -> 'b list
+end