Refactor Ci::Build#cache

app/models/ci/build.rb

@@ -461,11 +461,14 @@ module Ci
     end
 
     def cache
-      if options[:cache] && project.jobs_cache_index
-        options[:cache].merge(key: "#{options[:cache][:key]}:#{project.jobs_cache_index}")
-      else
-        [options[:cache]]
+      cache = options[:cache]
+
+      if cache && project.jobs_cache_index
+        cache = cache.merge(
+          key: "#{cache[:key]}:#{project.jobs_cache_index}")
       end
+
+      [cache]
     end
 
     def credentials