Update thread id validation returned by __wasi_thread_spawn

According to the documentation: https://github.com/WebAssembly/wasi-threads#design-choice-thread-ids, TID should be in the range <1, 0x1FFFFFFF>

libc-top-half/musl/src/thread/pthread_create.c

@@ -558,14 +558,18 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
 			__wait(&args->control, 0, 3, 0);
 	}
 #else
+#define WASI_THREADS_MIN_TID 1
+#define WASI_THREADS_MAX_TID 0x1FFFFFFF
 	/* `wasi_thread_spawn` will either return a host-provided thread ID (TID)
-	 * (`>= 0`) or an error code (`< 0`). As in the unmodified version, all
+	 * (`<1, 0x1FFFFFFF>`) or an error code (`< 0`). Please note that `0` is
+	 * reserved for compatibility reasons and must not be returned by the runtime
+	 * (if that happens, EAGAIN is returned). As in the unmodified version, all
 	 * spawn failures translate to EAGAIN; unlike the modified version, there is
 	 * no need to "start up" the child thread--the host does this. If the spawn
 	 * did succeed, then we store the TID atomically, since this parent thread
 	 * is racing with the child thread to set this field; this way, whichever
 	 * thread reaches this point first can continue without waiting. */
-	if (ret < 0) {
+	if (ret < WASI_THREADS_MIN_TID || ret > WASI_THREADS_MAX_TID) {
 		ret = -EAGAIN;
 	} else {
 		atomic_store((atomic_int *) &(new->tid), ret);