[CI] Allow pica-ci-base to fail to skip step when launching manually a Pipeline

.gitlab-ci.yml

@@ -45,6 +45,8 @@ pica-ci-base:
       changes:
         - "pica-ci-base/Dockerfile"
       when: manual
+      allow_failure: true
+    - when: never
 
 # Create a file a few environment variables added (which Dockerfile has been modified, the complete name of the image...)
 # The file will be an artifact shared with further steps