CI: dune is now necessary for the build

3 jobs for master in 11 seconds
Status Name Job ID Coverage
  Build
failed build_and_test #92589

00:00:11

 
  Test
skipped test_opam_test #92590
 
  Release
skipped release #92591
 
Name Stage Failure
failed
build_and_test Build There is an unknown failure, please try again
Using docker image ocaml/opam:ubuntu ID=sha256:a7fd6a58950edfc603f31774f309fc8de7ea309fcfc54eb7c9fee0f30b975951 for build container...
Running on runner-be4c7d9b-project-530-concurrent-0 via veri-gitlabrun...
Cloning repository...
Cloning into '/builds/verimag/synchrone/lutils'...
Checking out a0c7e86f as master...
Skipping Git submodules setup
$ opam install dune ocamlfind
[ERROR] No package named dune found.
ERROR: Job failed: exit code 1