Fix CI

Author: Sukant Hajra

Diff for: .github/workflows/ci.yml

@@ -8,11 +8,17 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - uses: cachix/install-nix-action@v26
+      with:
+        # REVISIT: Pinning because Nix hashes in flake.lock are inconsistent
+        # between 2.18.1 (current version in the latest stable release of NixOS)
+        # and 2.21.
+        install_url: https://releases.nixos.org/nix/nix-2.18.1/install
     - uses: cachix/cachix-action@v14
       with:
         name: shajra
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
     - uses: DeterminateSystems/magic-nix-cache-action@main
     - run: cat /etc/nix/nix.conf
     - run: cat ~/.config/nix/nix.conf
+    - run: nix --version
     - run: nix --print-build-logs build --print-out-paths .#ci