try cachix for CI

Author: georgefst

.github/workflows/haskell.yml

@@ -12,8 +12,13 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@main
-      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - uses: cachix/install-nix-action@v30
+        with:
+          github_access_token: ${{ secrets.GITHUB_TOKEN }}
+      - uses: cachix/cachix-action@v15
+        with:
+          name: georgefst
+          authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
 
       - name: Build all packages
         run: nix build .#ci