Add no-op default interception interface

This enables building for unsupported platforms

firewall/interception/interception_default.go

@@ -0,0 +1,18 @@
+//+build !windows,!linux
+
+package interception
+
+import (
+	"github.com/safing/portbase/log"
+)
+
+// start starts the interception.
+func start() error {
+	log.Info("interception: this platform has no support for packet interception - a lot of functionality will be broken")
+	return nil
+}
+
+// stop starts the interception.
+func stop() error {
+	return nil
+}