Update on "[ET-VK] Support setting cache_data_path at build time"

Differential Revision: [D75708084](https://our.internmc.facebook.com/intern/diff/D75708084/)

[ghstack-poisoned]

Author: jorgep31415

backends/vulkan/runtime/vk_api/Runtime.cpp

@@ -384,7 +384,7 @@ std::string& set_and_get_pipeline_cache_data_path(
 #if defined(ETVK_DEFAULT_CACHE_PATH)
   static std::string global_cache_data_path = ETVK_DEFAULT_CACHE_PATH;
 #else
-  static std::string global_cache_data_path = "";
+  static std::string global_cache_data_path;
 #endif /* ETVK_DEFAULT_CACHE_PATH */
 
   if (file_path.size() > 0) {