chore(oxcaml): CI with opam instead of nix

.github/workflows/workflow.yml

@@ -326,6 +326,34 @@ jobs:
       # - name: Build Dune
       # run: _boot/dune build dune.install
 
+  oxcaml:
+    name: Building Dune with OxCaml
+    needs: nix-build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Install OCaml
+        uses: ocaml/setup-ocaml@v3
+        with:
+          ocaml-compiler: ocaml-variants.5.2.0+ox
+          opam-repositories: |
+            oxcaml: "git+https://github.com/oxcaml/opam-repository.git"
+            default: "git+https://github.com/ocaml/opam-repository.git"
+          opam-pin: false
+
+      - name: Pin deps
+        run: opam pin add -n . --with-version=3.20.2+ox
+
+      - name: Install deps
+        run: opam install csexp pp re spawn uutf ./dune.opam
+
+      - name: Build dune
+        run: opam exec -- make bootstrap
+
+      - name: Run OxCaml tests
+        run: opam exec -- ./dune.exe test ./test/blackbox-tests/test-cases/oxcaml
+
   create-local-opam-switch:
     name: Create local opam switch
     needs: nix-build
@@ -370,25 +398,6 @@ jobs:
           gc-max-store-size-linux: 5G
       - run: nix develop .#microbench -c make dune build bench/micro
 
-  oxcaml-test:
-    name: OxCaml
-    needs: nix-build
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v5
-      - uses: nixbuild/nix-quick-install-action@v34
-        with:
-          nix_conf: ${{ env.EXTRA_NIX_CONFIG }}
-      - uses: nix-community/cache-nix-action@v6
-        with:
-          primary-key: |
-            nix-${{ runner.os }}-${{ github.job }}-${{ hashFiles('**/*.nix', '**/flake.lock') }}
-          restore-prefixes-first-match: nix-${{ runner.os }}-${{ github.job }}-
-          gc-max-store-size-linux: 2G
-      - run: |
-          nix develop .#ox-minimal -c ocaml --version
-          nix develop .#ox-minimal -c make test-ox
-
   utop-dev-tool-test:
     name: Test that the utop dev tool can be built and run
     runs-on: ubuntu-latest