Remove reference to std::filesystem in starter_test

There was no need since we have a function which does what we want
already and newer clang complains a bunch about using the experimental
filesystem code.

Change-Id: I50d6dac4f09b99529b01526f42f1ef5cca2d2cb5
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/starter/starter_test.cc b/aos/starter/starter_test.cc
index 3a61fe7..f434e84 100644
--- a/aos/starter/starter_test.cc
+++ b/aos/starter/starter_test.cc
@@ -1,5 +1,4 @@
 #include <csignal>
-#include <experimental/filesystem>
 #include <future>
 #include <thread>
 
@@ -8,6 +7,7 @@
 #include "aos/network/team_number.h"
 #include "aos/testing/path.h"
 #include "aos/testing/tmpdir.h"
+#include "aos/util/file.h"
 #include "gtest/gtest.h"
 #include "starter_rpc_lib.h"
 #include "starterd_lib.h"
@@ -23,7 +23,7 @@
     FLAGS_shm_base = shm_dir_;
 
     // Nuke the shm dir:
-    std::experimental::filesystem::remove_all(shm_dir_);
+    aos::util::UnlinkRecursive(shm_dir_);
   }
 
  protected: