add cache priv and pub key

.github/workflows/build-machines-and-homes.yml

@@ -10,6 +10,9 @@ env:
     experimental-features = nix-command flakes
     accept-flake-config = true
     system-features = nixos-test benchmark big-parallel kvm
+    secret-key-files = ~/cache-priv-key.pem
+    extra-substituters = https://nixcache.cy7.sh
+    extra-trusted-public-keys = nixcache.cy7.sh:DN3d1dt0wnXfTH03oVmTee4KgmdNdB0NY3SuzA8Fwx8=
   TERM: ansi
   AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
   AWS_SECRET_ACCESS_KEY: ${{ secrets. AWS_SECRET_ACCESS_KEY }}
@@ -36,6 +39,8 @@ jobs:
           remove-codeql: 'true'
           remove-docker-images: 'true'
           build-mount-path: /nix
+      - name: setup binary cache key
+        run: echo "${{ secrets.NIX_CACHE_SECRET_KEY }}" >> ~/cache-priv-key.pem
       - name: Install Nix
         uses: cachix/install-nix-action@v30
       - name: Sync repository
@@ -73,6 +78,8 @@ jobs:
           remove-codeql: 'true'
           remove-docker-images: 'true'
           build-mount-path: /nix
+      - name: setup binary cache key
+        run: echo "${{ secrets.NIX_CACHE_SECRET_KEY }}" >> ~/cache-priv-key.pem
       - name: Install Nix
         uses: cachix/install-nix-action@v30
       - name: Sync repository