Packaging a library with extra_objects

[Hirrolot]

(This is a continuation of my attempt to use a library with foreign C code.)

Run dune init proj --kind=library foo. Put the following support.c file in lib/:

#include <stdio.h>

void foo(void) {
    puts("foo");
}

lib/dune must look as follows:

(library
 (public_name foo)
 (name foo)
 (libraries ctypes.foreign)
 (extra_objects support))

(rule
 (targets support.o)
 (deps support.c)
 (action
  (run ocamlopt %{deps})))

lib/Foo.ml must be:

open Ctypes
open Foreign

let test = foreign "foo" (void @-> returning void)

Type dune build && dune install.

Then create a new project with dune init proj --kind=executable test with the following bin/dune:

(executable
 (public_name test)
 (name main)
 (libraries test foo))

and the following bin/main.ml:

open Foo

let () = test ()

Type dune exec test and see the following error:

File "bin/dune", line 3, characters 7-11:
3 |  (name main)
           ^^^^
/usr/bin/ld: cannot find lib/support.o: No such file or directory
collect2: error: ld returned 1 exit status
File "caml_startup", line 1:
Error: Error during linking (exit code 1)

Is there a way to tell Dune to link support.o with the executable? If I call Foo.test from within foo's tests, everything seems to work fine.

Specifications

$ dune --version
3.15.0
$ ocamlc --version
5.1.2+dev0-2023-12-7

My OS is Ubuntu 22.04 jammy (x86_64 Linux 6.5.0-28-generic).