Add SSH host key to environment before rsync-ing

.gitlab-ci.yml

@@ -17,6 +17,8 @@ deploy-prod:
   - apk add rsync
   - bundle install
   - jekyll build -d public
+  - mkdir -p "$HOME/.ssh"
+  - echo "$SSH_KNOWN_HOSTS" > "$HOME/.ssh/known_hosts"
   - rsync -e "ssh -i $SSH_DEPLOY_KEY" --delete-after -rlptP public/ "$SSH_DEPLOY_USER@$SSH_DEPLOY_HOST:/www.poul.org/"
   cache:
     key: gems