Add -k option to opam pin

.gitlab-ci.yml

@@ -504,7 +504,7 @@ ocaml-versions-nightly:
   image: 'ocaml/opam:ubuntu-20.04-ocaml-$OCAML'
   script:
     - sudo apt update
-    - opam pin . -n
+    - opam pin . -n -k path
     - opam depext frama-c --with-test
     - opam install --jobs 2 frama-c --with-test --with-doc
     - frama-c --plugins