Actually comment the new tests

libstdc++-v3/testsuite/29_atomics/atomic_flag/test/explicit.cc

+// { dg-do run { target c++2a } }
+// { dg-require-thread-fence "" }
+
+// Copyright (C) 2008-2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <atomic>
+
+int main()
+{
+  using namespace std;
+  atomic_flag af = ATOMIC_FLAG_INIT;
+
+  if (af.test(memory_order_acquire))
+    af.clear(memory_order_release);
+
+  return 0;
+}

libstdc++-v3/testsuite/29_atomics/atomic_flag/test/implicit.cc

+// { dg-do run { target c++2a } }
+// { dg-require-thread-fence "" }
+
+// Copyright (C) 2008-2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <atomic>
+
+int main()
+{
+  using namespace std;
+  atomic_flag af = ATOMIC_FLAG_INIT;
+
+  if (af.test())
+    af.clear();
+
+  return 0;
+}