[polari/wip/fmuellner/ci-snapshots] ci: Set a cache key

[Florian Müllner <fmuellner src gnome org>]

commit 006e08e2fca909c900c66004c377cfc6715e01d0
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Jul 25 19:42:11 2018 +0200

    ci: Set a cache key
    
    Maybe that'll convince gitlab to not throw away the cache?!

 .gitlab-ci.yml | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 765b7cd..28f9ce9 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -42,6 +42,7 @@ flatpak:
             - _build/meson-logs/testlog.txt
         expire_in: 30 days
     cache:
+        key: flatpak-builder
         paths:
              - cache.tar.gz