qemu/thread: Mark qemu_thread_exit() with 'noreturn' attribute
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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>