c++17: drop experimental::filesystem

Use the real filesystem library, and drop support for building with
experimental under c++14.

Signed-off-by: Jayanth Othayoth <ojayanth@in.ibm.com>
Change-Id: I730c0d6dce53b5e0aa0867cddb7f325cdb9b45fc
diff --git a/dump_serialize.hpp b/dump_serialize.hpp
index 8ad4a24..8fc4d14 100644
--- a/dump_serialize.hpp
+++ b/dump_serialize.hpp
@@ -2,7 +2,7 @@
 
 #include "config.h"
 
-#include <experimental/filesystem>
+#include <filesystem>
 #include <set>
 
 namespace phosphor
@@ -14,22 +14,21 @@
 using EId = uint32_t;
 using ElogList = std::set<EId>;
 
-namespace fs = std::experimental::filesystem;
-
 /** @brief Serialize and persist list of ids.
  *  @param[in] list - elog id list.
  *  @param[in] dir - pathname of file where the serialized elog id's will
  *                   be placed.
  */
 void serialize(const ElogList& list,
-               const fs::path& dir = fs::path(ELOG_ID_PERSIST_PATH));
+               const std::filesystem::path& dir =
+                   std::filesystem::path(ELOG_ID_PERSIST_PATH));
 
 /** @brief Deserialze a persisted list of ids into list
  *  @param[in] path - pathname of persisted error file
  *  @param[out] list - elog id list
  *  @return bool - true if the deserialization was successful, false otherwise.
  */
-bool deserialize(const fs::path& path, ElogList& list);
+bool deserialize(const std::filesystem::path& path, ElogList& list);
 
 } // namespace elog
 } // namespace dump