Add a stub for pthread_once

expected/wasm32-wasip1/defined-symbols.txt

@@ -1002,6 +1002,7 @@ pthread_mutexattr_setprotocol
 pthread_mutexattr_setpshared
 pthread_mutexattr_setrobust
 pthread_mutexattr_settype
+pthread_once
 pthread_rwlock_destroy
 pthread_rwlock_init
 pthread_rwlock_rdlock

expected/wasm32-wasip2/defined-symbols.txt

@@ -1135,6 +1135,7 @@ pthread_mutexattr_setprotocol
 pthread_mutexattr_setpshared
 pthread_mutexattr_setrobust
 pthread_mutexattr_settype
+pthread_once
 pthread_rwlock_destroy
 pthread_rwlock_init
 pthread_rwlock_rdlock

stub-pthreads/stub-pthreads-good.c

@@ -7,3 +7,12 @@ static void dummy_0()
 }
 weak_alias(dummy_0, __acquire_ptc);
 weak_alias(dummy_0, __release_ptc);
+
+int pthread_once(pthread_once_t *control, void (*init)(void))
+{
+	if (!*control) {
+		init();
+		*control = 1;
+	}
+	return 0;
+}