split continuous integration in two steps

.gitlab-ci.yml

-tests_with_recompilation:
+stages:
+  - build
+  - test
+
+build:
   image: ocaml/opam@sha256:aabf10d76f588677f6ee8007aae3d4dd45d28000501abce5aabda9de50e88dc7
+  stage: build
   script:
    - sudo apt-get update
-   - sudo apt-get install -y make parallel libgmp-dev
+   - sudo apt-get install -y make libgmp-dev
    - opam install dune.3.12.1 fmt.0.9.0 gen.1.1 menhir.20230608 ocplib-simplex.0.5 parsexp.v0.16.0 spelll.0.4 uutf.1.0.3 zarith.1.13
    - make clean
    - make clean_bundle
    - make
    - make bundle
-   - make test
   artifacts:
     paths:
-     - logs
      - bundle
     expire_in: 1 week
   tags:
     - docker
+
+test:
+  image: debian@sha256:7ceacc4462a98718b236cbdeb850d4b7603afe4bab791336a0ed1c030f769f02
+  stage: test
+  needs: [build]
+  script:
+    - apt-get update
+    - apt-get install -y make parallel
+    - make test
+  artifacts:
+    paths:
+      - logs
+    expire_in: 1 week
+  tags:
+    - docker
+