設定 Linux 防火牆規則，允許 Fuchsia 裝置和模擬器流量。
Setup Linux firewall via iptables to allow Fuchsia device and emulator traffic.
This command detects whether iptables is installed,
and if so, will add special rules to allow Fuchsia-specific traffic to
go through the link-local IPv6 network interfaces used by Fuchsia devices
and emulators. If `ufw` (Uncomplicated Firewall) is installed on the system,
we will abort, and recommend the script `fx setup-ufw`.
NOTE: This script uses sudo and will thus ask for your password!
-n|--dry-run Just print all steps, don't do any configuration
-u|--undo Remove all firewall rules installed by this script