ci: revert cache-nix-action to version 4.0.3

.forgejo/workflows/check.yml

@@ -24,20 +24,20 @@ jobs:
           echo "hash=$(md5sum flake.lock | awk '{print $1}')" >> $GITHUB_OUTPUT
 
       - name: Restore and cache Nix store
-        uses: https://github.com/nix-community/cache-nix-action@v5
+        uses: https://github.com/nix-community/cache-nix-action@v4.0.3
         id: nix-store-cache
         with:
-          primary-key: cache-${{ runner.os }}-nix-store-${{ steps.flake-lock-hash.outputs.hash }}
-          restore-prefixes-first-match: |
+          key: cache-${{ runner.os }}-nix-store-${{ steps.flake-lock-hash.outputs.hash }}
+          restore-keys: |
             cache-${{ runner.os }}-nix-store-
 
           gc-linux: true
           gc-max-store-size-linux: 10000000000
 
-          purge: true
-          purge-prefixes: cache-${{ runner.os }}-nix-store-
-          purge-created: 42
-          purge-primary-key: never
+          purge-caches: true
+          purge-key: cache-${{ runner.os }}-nix-store-
+          purge-created: true
+          purge-created-max-age: 42
 
       - name: Prepare cachix
         uses: https://github.com/cachix/cachix-action@v14
@@ -49,3 +49,12 @@ jobs:
       - name: Run flake checks
         run: |
           nix --print-build-logs --verbose --accept-flake-config --access-tokens '' flake check
+          # Prevent cache garbage collection
+          for target in $(nix flake show --json --all-systems | jq '
+            .["nixosConfigurations"] |
+            to_entries[] |
+            .key
+            ' | tr -d '"'
+          ); do
+            nix profile install --profile "/nix/var/nix/profiles/$target" ".#nixosConfigurations.${target}.config.system.build.toplevel"
+          done