Update '.drone.yml'

.drone.yml

@@ -10,6 +10,8 @@ steps:
           from_secret: ssh-priv
         SSH_PUB:
           from_secret: ssh-pub
+        KNOWN_HOSTS:
+          from_secret: known-hosts # this is just $(ssh-keyscan leonetienne.de)
       commands:
         - cd "GCryptLib/doxygen"
         - apt-get update
@@ -23,8 +25,10 @@ steps:
         - mkdir -p ~/.ssh
         - echo "$SSH_PRIV" > ~/.ssh/id_ed25519
         - echo "$SSH_PUB" > ~/.ssh/id_ed25519.pub
+        - echo "$KNOWN_HOSTS" > ~/.ssh/known_hosts
         - chmod 600 ~/.ssh/id_ed25519
         - chmod 644 ~/.ssh/id_ed25519.pub
+        - chmod 644 ~/.ssh/known_hosts
         - ssh-add
         - >-
           rsync