Add auto_route and auto_detect_interface for linux

common/iffmonitor/monitor_other.go

@@ -0,0 +1,13 @@
+//go:build !linux
+
+package iffmonitor
+
+import (
+	"os"
+
+	"github.com/sagernet/sing-box/log"
+)
+
+func New(logger log.Logger) (InterfaceMonitor, error) {
+	return nil, os.ErrInvalid
+}