Speedup static build by utilizing CI cache on /nix folder

Signed-off-by: Wong Hoi Sing Edison <[email protected]>

.cirrus.yml

@@ -229,19 +229,36 @@ static_binary_task:
     depends_on:
         - 'config'
         - 'fmt'
+
     gce_instance:
         image_name: "${FEDORA_CACHE_IMAGE_NAME}"
         cpu: 8
         memory: 12
         disk: 200
-    script: |
+
+    init_script: |
         set -ex
         setenforce 0
         growpart /dev/sda 1 || true
         resize2fs /dev/sda1 || true
         yum -y install podman
+
+    nix_cache:
+      folder: '.cache'
+      reupload_on_changes: true
+      fingerprint_script: |
+        echo "nix-v8-$(sha1sum nix/nixpkgs.json | head -c 40)"
+      populate_script: |
+        mkdir -p .cache
+
+    build_script: |
+        set -ex
         mkdir -p /nix
-        podman run --rm --privileged -ti -v /:/mnt nixos/nix cp -rfT /nix /mnt/nix
-        podman run --rm --privileged -ti -v /nix:/nix -v ${PWD}:${PWD} -w ${PWD} nixos/nix nix --print-build-logs --option cores 8 --option max-jobs 8 build --file nix/
+        if [[ ! -z $(ls -A .cache) ]]; then rsync -aq --delete .cache/ /nix; else podman run --rm --privileged -v /:/mnt nixos/nix cp -rfT /nix /mnt/nix; fi
+        podman run --rm --privileged -v /nix:/nix -v ${PWD}:${PWD} -w ${PWD} nixos/nix nix --option cores 8 --option max-jobs 8 build --file nix/
+        mkdir -p .cache
+        rsync -aq --delete /nix/ .cache
+        chown -Rf $(whoami) .cache
+
     binaries_artifacts:
         path: "result/bin/conmon"