main/poll: Record wait() error on every backend

php_poll_wait() reported a stale error code when a backend's wait syscall
failed without recording one: epoll, poll and kqueue returned -1 without
setting it. Record it from errno in those backends so php_poll_get_error()
reflects the actual failure. eventport and wsapoll already did, the
latter from WSAGetLastError().

Closes GH-22326

Author: iliaal

main/poll/poll_backend_epoll.c

@@ -195,6 +195,8 @@ static int epoll_backend_wait(
 			events[i].revents = epoll_events_from_native(backend_data->events[i].events);
 			events[i].data = backend_data->events[i].data.ptr;
 		}
+	} else if (nfds < 0) {
+		php_poll_set_current_errno_error(ctx);
 	}
 
 	return nfds;

main/poll/poll_backend_kqueue.c

@@ -320,6 +320,11 @@ static int kqueue_backend_wait(
 	int nfds = kevent(
 			backend_data->kqueue_fd, NULL, 0, backend_data->events, required_capacity, timeout);
 
+	if (nfds < 0) {
+		php_poll_set_current_errno_error(ctx);
+		return -1;
+	}
+
 	if (nfds > 0) {
 		if (ctx->raw_events) {
 			/* Raw events mode - direct 1:1 mapping, no grouping */

main/poll/poll_backend_poll.c

@@ -215,8 +215,11 @@ static int poll_backend_wait(
 	int timeout_ms = php_poll_timespec_to_ms(timeout);
 	int nfds = poll(backend_data->temp_fds, fd_count, timeout_ms);
 
-	if (nfds <= 0) {
-		return nfds; /* Return 0 for timeout, -1 for error */
+	if (nfds < 0) {
+		php_poll_set_current_errno_error(ctx);
+		return -1;
+	} else if (nfds == 0) {
+		return 0; /* timeout */
 	}
 
 	/* Process results - iterate through struct pollfd array directly */