CI: Add dependency between prepare_environment and build

* Explicitly make build depend on prepare_environmnt, so it will fail
when the artifacts of prepare_environment are missing
* Increase timeout of prepare_environment artifacts

.gitlab-ci-template.yml

@@ -59,7 +59,7 @@ prepare_environment:
     - *checkout_commit
     - *repo_tag
   artifacts:
-    expire_in: 3h
+    expire_in: 1d
     paths:
       - "./"
   cache:
@@ -81,6 +81,8 @@ prepare_environment:
     SETUPSCRIPT: "setup-environment"
     IMAGEPATH: "tmp/deploy/images"
     INSTALLSCRIPT: "fng-install.sh"
+  dependencies:
+    - prepare_environment
   before_script:
     - *setup_ssh
   script: