xtensa: add a stub user.h file

Xtensa only supports the ELF binary format, so the user.h file isn't
needed. However, it's included by other files, so provide a stub user.h.

Signed-off-by: Chris Zankel <chris@zankel.net>

libc/sysdeps/linux/xtensa/sys/user.h

@@ -0,0 +1,20 @@
+/*
+ * include/asm-xtensa/user.h
+ *
+ * Xtensa Processor version.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001 - 2005 Tensilica Inc.
+ */
+
+#ifndef _XTENSA_USER_H
+#define _XTENSA_USER_H
+
+/* This file usually defines a 'struct user' structure. However, it it only
+ * used for a.out file, which are not supported on Xtensa.
+ */
+
+#endif  /* _XTENSA_USER_H */