Fix CI build and keep snapshots out of version control

The snapshots/create-index.sh script now "creates" the directory.

.gitignore

@@ -1,2 +1,3 @@
 *~
-
+snapshots/*.tar.gz
+snapshots/index.html

.gitlab-ci.yml

@@ -9,7 +9,6 @@ pages:
   - mkdir .public
   - mv * .public/
   - mv .public public
-  - mkdir public/snapshots
   - wget --quiet -O public/snapshots/sane-backends-git$(date +%F).tar.gz $URL/backends/repository/master/archive.tar.gz
   - wget --quiet -O public/snapshots/sane-frontends-git$(date +%F).tar.gz $URL/frontends/repository/master/archive.tar.gz
   - wget --quiet -O backends.zip $URL/backends/-/jobs/artifacts/master/download?job=archive