MDX does not rebuild when the prelude changes

[talex5]

Expected Behavior

When using (mdx (preludes prelude.ml) ...), changing prelude.ml should cause the tests to be run again.

Actual Behavior

It ignores this and you have to do dune clean first.

Reproduction

$ ls
dune  dune-project  prelude.ml  README.md

$ cat dune
(mdx
  (preludes prelude.ml)
  (files README.md))

$ cat dune-project 
(lang dune 3.6)
(using mdx 0.3)

$ cat prelude.ml 
let foo () = 1

$ cat README.md 
```ocaml
# foo();;
- : int = 1

$ dune runtest

$ echo 'let foo () = 2' > prelude.ml
$ dune runtest

$ dune clean; dune runtest
File "README.md", line 1, characters 0-0:
...

Specifications

• Version of dune (output of dune --version): 3.6.2
• Version of ocaml (output of ocamlc --version): 5.0.0
• Operating system (distribution and version): Debian 11

[emillon]

Confirmed from a quick look at the source code. I'll prepare a PR.