This is needed to run Python on the Hurd, especially during the build of
python-boot0.

Adapted from https://salsa.debian.org/glibc-team/glibc/-/blob/glibc-2.31/debian/patches/hurd-i386/unsubmitted-clock_t_centiseconds.diff

Use the realtime clock for the monotonic clock. This is of course not a proper
implementation (which is being done in Mach), but will permit to fix at least
the iceweasel stack.

vlc however doesn't build when _POSIX_CLOCK_SELECTION is enabled but
_POSIX_TIMERS is not, and they refuse to fix that (see #765578), so disable the
former.

From 0aa1dfd580cf9ad7b812c307b128decb782b825f Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Mon, 2 Mar 2020 18:59:04 +0100
Subject: [PATCH 2/2] Use realtime clock for the monotonic clock.

---
 sysdeps/mach/clock_gettime.c       | 2 +-
 sysdeps/mach/hurd/bits/posix_opt.h | 6 +++---
 sysdeps/posix/clock_getres.c       | 1 +
 sysdeps/pthread/timer</td></tr></table>
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