use filesystem instead of experimental

Use filesystem now that it should be available instead of
experimental::filesystem.

Change-Id: I8648ac2b279eea42c13d6b12f312a2e1e02aa152
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/configure.ac b/configure.ac
index f77953a..b7f743f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -46,11 +46,6 @@
     [AC_MSG_ERROR([Could not find libipmid...openbmc/phosphor-host-ipmid package required])]
 )
 AC_CHECK_HEADER(
-    experimental/filesystem,
-    [],
-    [AC_MSG_ERROR([Could not find experimental/filesystem...libstdc++fs development package required])]
-)
-AC_CHECK_HEADER(
     nlohmann/json.hpp,
     [],
     [AC_MSG_ERROR([Could not find nlohmann/json.hpp])]
diff --git a/sysfs/util.cpp b/sysfs/util.cpp
index aeceada..d73ec0f 100644
--- a/sysfs/util.cpp
+++ b/sysfs/util.cpp
@@ -16,7 +16,7 @@
 
 #include "sysfs/util.hpp"
 
-#include <experimental/filesystem>
+#include <filesystem>
 #include <iostream>
 #include <string>
 
@@ -31,7 +31,7 @@
  */
 
 static constexpr auto platform = "/sys/devices/platform/";
-namespace fs = std::experimental::filesystem;
+namespace fs = std::filesystem;
 
 std::string FixupPath(std::string original)
 {