warnings in windows ci logs

[raphael-proust]

In job https://github.com/ocaml/opam-repository/actions/runs/10065951645/job/27826207735?pr=26276 the following warnings appear (in the "Install package" phase):

  [WARNING] .install file is missing .exe extension for src/findlib/ocamlfind
  [WARNING] .install file is missing .exe extension for src/findlib/ocamlfind_opt
  [WARNING] Automatically adding .exe to D:\opamroot\default\.opam-switch\build\ocamlfind.1.9.5\src\findlib\ocamlfind.exe
  [WARNING] Automatically adding .exe to D:\opamroot\default\.opam-switch\build\ocamlfind.1.9.5\src\findlib\ocamlfind_opt.exe
  [WARNING] D:\opamroot\default\bin\safe_camlp4 is a script; the command won't be available

Similar in https://github.com/ocaml/opam-repository/actions/runs/10058272252/job/27800985660?pr=26274

Similar in https://github.com/ocaml/opam-repository/actions/runs/10062908336/job/27816477610?pr=26271

It's not causing failures, but it might be worth investigating.