package/ntp: Fix building with glibc 2.34+

On attempt to build ntp with glibc 2.34 the following error happens:
-------------------------------->8------------------------------
In file included from .../output/host/lib/gcc/i586-buildroot-linux-gnu/10.3.0/include-fixed/pthread.h:42,
                 from work_thread.c:13:
work_thread.c:45:57: error: missing binary operator before token "("
   45 | #if defined(PTHREAD_STACK_MIN) && THREAD_MINSTACKSIZE < PTHREAD_STACK_MIN
      |                                                         ^~~~~~~~~~~~~~~~~
-------------------------------->8------------------------------

That's because starting from glibc 2.34 PTHREAD_STACK_MIN gets determined
dynamically in runtime via sysconf(), see [1].

Original fix proposed by Khem Raj in OpenEmbedded, see [2].

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=5d98a7dae955bafa6740c26eaba9c86060ae0344
[2] https://github.com/openembedded/meta-openembedded/commit/7055c764c83150f9310ce04bcfb19330460582fc

Suggested-by: Artem Panfilov <artemp@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/ntp/0004-libntp-Do-not-use-PTHREAD_STACK_MIN-on-glibc.patch

@@ -0,0 +1,33 @@
+From 082a504cfcc046c3d8adaae1164268bc94e5108a Mon Sep 17 00:00:00 2001
+From: Khem Raj <raj.khem@gmail.com>
+Date: Sat, 31 Jul 2021 10:51:41 -0700
+Subject: [PATCH] libntp: Do not use PTHREAD_STACK_MIN on glibc
+
+In glibc 2.34+ PTHREAD_STACK_MIN is not a compile-time constant which
+could mean different stack sizes at runtime on different architectures
+and it also causes compile failure. Default glibc thread stack size
+or 64Kb set by ntp should be good in glibc these days.
+
+Signed-off-by: Khem Raj <raj.khem@gmail.com>
+[Copied from https://github.com/openembedded/meta-openembedded/blob/master/meta-networking/recipes-support/ntp/ntp/0001-libntp-Do-not-use-PTHREAD_STACK_MIN-on-glibc.patch]
+Signed-off-by: Alexey Brodkin <abrokdin@synopsys.com>
+---
+ libntp/work_thread.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/libntp/work_thread.c b/libntp/work_thread.c
+index 03a5647..3ddd751 100644
+--- a/libntp/work_thread.c
++++ b/libntp/work_thread.c
+@@ -41,7 +41,7 @@
+ #ifndef THREAD_MINSTACKSIZE
+ # define THREAD_MINSTACKSIZE	(64U * 1024)
+ #endif
+-#ifndef __sun
++#if !defined(__sun) && !defined(__GLIBC__)
+ #if defined(PTHREAD_STACK_MIN) && THREAD_MINSTACKSIZE < PTHREAD_STACK_MIN
+ # undef THREAD_MINSTACKSIZE
+ # define THREAD_MINSTACKSIZE PTHREAD_STACK_MIN
+-- 
+2.32.0
+