Work around permission issues with caching action

.github/workflows/deploy.yml

@@ -17,11 +17,19 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Cache Nix downloads
+        id: nix-store-cache
         uses: actions/cache@v3
         with:
-          path: /nix/store
+          path: /tmp/nix-cache
           key: nix-store-${{ hashFiles('flake.nix', 'flake.lock', 'shell.nix') }}
 
+      - name: Restore Nix downloads cache
+        if: steps.nix-store-cache.outputs.cache-hit == 'true'
+        run: |
+          sudo rm -rf /nix
+          sudo mv /tmp/nix-cache /nix
+          sudo chown -R root /nix
+
       - name: Cache Nodejs downloads
         uses: actions/cache@v3
         with:
@@ -58,3 +66,9 @@ jobs:
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           force_orphan: true
+
+      - name: Copy Nix store to cachable location
+        if: steps.nix-store-cache.outputs.cache-hit != 'true'
+        run: |
+          sudo cp -r --preserve=timestamps /nix /tmp/nix-cache
+          sudo rm -rf /tmp/nix-cache/var/nix/{daemon-socket/socket,userpool,gc.lock,db/big-lock,db/reserved}