Upgrade to 2022-era LLVM LIBCXX

third_party/libcxx/__support/ibm/nanosleep.h

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+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___SUPPORT_IBM_NANOSLEEP_H
+#define _LIBCPP___SUPPORT_IBM_NANOSLEEP_H
+
+#include <unistd.h>
+
+inline int nanosleep(const struct timespec* __req, struct timespec* __rem) {
+  // The nanosleep() function is not available on z/OS. Therefore, we will call
+  // sleep() to sleep for whole seconds and usleep() to sleep for any remaining
+  // fraction of a second. Any remaining nanoseconds will round up to the next
+  // microsecond.
+  if (__req->tv_sec < 0 || __req->tv_nsec < 0 || __req->tv_nsec > 999999999) {
+    errno = EINVAL;
+    return -1;
+  }
+  long __micro_sec = (__req->tv_nsec + 999) / 1000;
+  time_t __sec = __req->tv_sec;
+  if (__micro_sec > 999999) {
+    ++__sec;
+    __micro_sec -= 1000000;
+  }
+  __sec = static_cast<time_t>(sleep(static_cast<unsigned int>(__sec)));
+  if (__sec) {
+    if (__rem) {
+      // Updating the remaining time to sleep in case of unsuccessful call to sleep().
+      __rem->tv_sec = __sec;
+      __rem->tv_nsec = __micro_sec * 1000;
+    }
+    errno = EINTR;
+    return -1;
+  }
+  if (__micro_sec) {
+    int __rt = usleep(static_cast<unsigned int>(__micro_sec));
+    if (__rt != 0 && __rem) {
+      // The usleep() does not provide the amount of remaining time upon its failure,
+      // so the time slept will be ignored.
+      __rem->tv_sec = 0;
+      __rem->tv_nsec = __micro_sec * 1000;
+      // The errno is already set.
+      return -1;
+    }
+    return __rt;
+  }
+  return 0;
+}
+
+#endif // _LIBCPP___SUPPORT_IBM_NANOSLEEP_H