ARC: Thread Local Storage support

This includes all 4 TLS addressing models

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

sysdeps/arc/stackinfo.h

@@ -0,0 +1,33 @@
+/* Stack environment definitions for ARC.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* This file contains a bit of information about the stack allocation
+   of the processor.  */
+
+#ifndef _STACKINFO_H
+#define _STACKINFO_H	1
+
+#include <elf.h>
+
+/* On ARC the stack grows down.  */
+#define _STACK_GROWS_DOWN	1
+
+/* Default to a non-executable stack.  */
+#define DEFAULT_STACK_PERMS (PF_R|PF_W)
+
+#endif	/* stackinfo.h */