Run job manually and not on every commit

.gitlab-ci.yml

@@ -6,6 +6,8 @@ build-zynthbox-image-armhf:
     - arm64
   image: ubuntu:22.04@sha256:cb6ce0db39adc371523a22a0031aa978ad3efbb13a279b7608010c82f8ab214e
   stage: build
+  rules:
+    - when: manual
   script:
     - set -x