Add nvptx port.

- From: Cesar Philippidis <cesar@codesourcery.com>
  Date: Tue, 10 Apr 2018 14:43:42 -0700
  Subject: [PATCH] nvptx port

  This port adds support for Nvidia GPU's, which are primarily used as
  offload accelerators in OpenACC and OpenMP.

newlib/libc/machine/nvptx/misc.c

@@ -0,0 +1,34 @@
+/*
+ * Support file for nvptx in newlib.
+ * Copyright (c) 2014-2018 Mentor Graphics.
+ *
+ * The authors hereby grant permission to use, copy, modify, distribute,
+ * and license this software and its documentation for any purpose, provided
+ * that existing copyright notices are retained in all copies and that this
+ * notice is included verbatim in any distributions. No written agreement,
+ * license, or royalty fee is required for any of the authorized uses.
+ * Modifications to this software may be copyrighted by their authors
+ * and need not follow the licensing terms described here, provided that
+ * the new terms are clearly indicated on the first page of each file where
+ * they apply.
+ */
+
+#include <errno.h>
+#include <sys/types.h>
+#undef errno
+extern int errno;
+
+int
+close(int fd) {
+  return -1;
+}
+
+off_t
+lseek(int fd, off_t offset, int whence) {
+  return 0;
+}
+
+int
+read(int fd, void *buf, size_t count) {
+  return 0;
+}