[RFC PATCH] qemu/thread: Mark qemu_thread_exit() with 'noreturn' attribute

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

After upgrading to Ubuntu 20.04 LTS, GCC 9.3 complains:

  util/qemu-thread-posix.c: In function ‘qemu_thread_exit’:
  util/qemu-thread-posix.c:577:6: error: function might be candidate for attribute ‘noreturn’ [-Werror=suggest-attribute=noreturn]
    577 | void qemu_thread_exit(void *retval)
        |      ^~~~~~~~~~~~~~~~

Fix by marking the qemu_thread_exit function with QEMU_NORETURN
to set the 'noreturn' attribute.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
RFC because I'm not sure the error is correct, or we should
simply ignore it by default with -Wno-suggest-attribute=noreturn.
---
 include/qemu/thread.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index d22848138e..06c058fb58 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -177,7 +177,7 @@ void qemu_thread_create(QemuThread *thread, const char *name,
 void *qemu_thread_join(QemuThread *thread);
 void qemu_thread_get_self(QemuThread *thread);
 bool qemu_thread_is_self(QemuThread *thread);
-void qemu_thread_exit(void *retval);
+void qemu_thread_exit(void *retval) QEMU_NORETURN;
 void qemu_thread_naming(bool enable);
 
 struct Notifier;
-- 
2.21.3