[libstdc++] Use __gthread_join in jthread/95989

[Alexandre Oliva <oliva@adacore.com>]

Ref: https://gcc.gnu.org/pipermail/gcc-patches/2021-May/570617.html

Bernd Edlinger <bernd.edlinger@hotmail.de> reported that the 95989.cc
test fails without pthread_join at the end of main, but pthread_join
is no good for a test that doesn't require pthreads.

This patch adds a __gthread_join call instead.

Regstrapped on x86_64-linux-gnu.
Tested on arm-vxworks7 (gcc-12) and arm-eabi (trunk).  Ok to install?

for  libstdc++-v3/ChangeLog

	* testsuite/30_threads/jthread/95989.cc (main): Call
	__gthread_join at the end.
---
 libstdc++-v3/testsuite/30_threads/jthread/95989.cc |    1 +
 1 file changed, 1 insertion(+)

diff --git a/libstdc++-v3/testsuite/30_threads/jthread/95989.cc b/libstdc++-v3/testsuite/30_threads/jthread/95989.cc
index e98836d094531..407b52748438c 100644
--- a/libstdc++-v3/testsuite/30_threads/jthread/95989.cc
+++ b/libstdc++-v3/testsuite/30_threads/jthread/95989.cc
@@ -52,4 +52,5 @@ main()
   test01();
   test02();
   test03();
+  __gthread_join(0, NULL);
 }

-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
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