Update .gitlab-ci.yml

.gitlab-ci.yml

 stages:
+  - prepare
   - deploy
 
 variables:
@@ -8,6 +9,13 @@ variables:
   BUILD_ENV: test-build
   OP: update
 
+copy-files-to-swift:
+  stage: prepare
+  script:
+    - curl -H "X-Auth-Token: $OS_TOKEN" -X DELETE $OBJSTORE/ebrains-spack-builds.tar.gz
+    - tar czf ebrains-spack-builds.tar.gz packages/ repo.yml spack.yaml
+    - curl -H "X-Auth-Token: $OS_TOKEN" -i $OBJSTORE/ -X PUT -T ebrains-spack-builds.tar.gz
+
 deploy-build-environment:
   stage: deploy
   before_script: