Pin dune

Author: vouillon

.github/workflows/build.yml

@@ -112,6 +112,10 @@ jobs:
           dune-cache: true
           opam-pin: false
 
+      - name: Pin dune
+        run: |
+          opam pin add dune.3.17 https://github.com/ocaml/dune.git#3.17
+
       - run: opam install conf-pkg-config
         if: runner.os == 'Windows'