cmd/rootlessport: add missing linux build tags

This amends commit 772ead253 ("Use simulated dual-stack binds when using WSL")
which started using linux tag but not for all files.

Alas, this breaks ginkgo run on Windows, so add an exclusion.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

cmd/rootlessport/wsl.go

@@ -1,3 +1,5 @@
+//go:build linux
+
 package main
 
 import (

cmd/rootlessport/wsl_test.go

@@ -1,3 +1,5 @@
+//go:build linux
+
 package main
 
 import (