sandbox: support vsock connection to task api

Signed-off-by: Abel Feng <fshb1988@gmail.com>

vendor/github.com/mdlayher/socket/accept.go

@@ -0,0 +1,23 @@
+//go:build !dragonfly && !freebsd && !illumos && !linux
+// +build !dragonfly,!freebsd,!illumos,!linux
+
+package socket
+
+import (
+	"fmt"
+	"runtime"
+
+	"golang.org/x/sys/unix"
+)
+
+const sysAccept = "accept"
+
+// accept wraps accept(2).
+func accept(fd, flags int) (int, unix.Sockaddr, error) {
+	if flags != 0 {
+		// These operating systems have no support for flags to accept(2).
+		return 0, nil, fmt.Errorf("socket: Conn.Accept flags are ineffective on %s", runtime.GOOS)
+	}
+
+	return unix.Accept(fd)
+}