Store: Use SharedSync for state

src/libstore/store-api.cc

@@ -920,7 +920,7 @@ StorePathSet Store::exportReferences(const StorePathSet & storePaths, const Stor
 const Store::Stats & Store::getStats()
 {
     {
-        auto state_(state.lock());
+        auto state_(state.read());
         stats.pathInfoCacheSize = state_->pathInfoCache.size();
     }
     return stats;

src/libstore/store-api.hh

@@ -201,7 +201,7 @@ protected:
         LRUCache<std::string, PathInfoCacheValue> pathInfoCache;
     };
 
-    Sync<State> state;
+    SharedSync<State> state;
 
     std::shared_ptr<NarInfoDiskCache> diskCache;