Add Exn.raise_with_backtrace

src/stdune/exn.ml

@@ -10,3 +10,13 @@ let protectx x ~f ~finally =
   | exception e -> finally x; raise e
 
 let protect ~f ~finally = protectx () ~f ~finally
+
+include
+  ((struct
+    [@@@warning "-32-3"]
+    let raise_with_backtrace exn _ = reraise exn
+    include Printexc
+    let raise_with_backtrace exn bt = raise_with_backtrace exn bt
+  end) : (sig
+     val raise_with_backtrace: exn -> Printexc.raw_backtrace -> _
+   end))

src/stdune/exn.mli

@@ -8,3 +8,5 @@ external reraise       : exn -> _ = "%reraise"
 
 val protect : f:(unit -> 'a) -> finally:(unit -> unit) -> 'a
 val protectx : 'a -> f:('a -> 'b) -> finally:('a -> unit) -> 'b
+
+val raise_with_backtrace: exn -> Printexc.raw_backtrace -> _