Fix .drone.yml again

.drone.yml

@@ -5,6 +5,15 @@ type: docker
 name: default
 
 steps:
+  - name: load cache ssh key
+    image: alpine:3.17
+    commands:
+      - mkdir -p .ssh
+      - echo "$CACHE_SSH_KEY" > .ssh/id_cache
+    environment:
+      CACHE_SSH_KEY:
+        from_secret: cache_ssh_key
+
   - name: restore cache
     image: meltwater/drone-cache
     environment: &cache_env
@@ -16,8 +25,7 @@ steps:
         backend: sftp
         mount:
           - resources/_gen
-        public_key_file:
-          from_secret: cache_ssh_key
+        public_key_file: .ssh/id_cache
         username: u194355-sub5
       restore: yes