all: fix some js/wasm compilation issues

Change-Id: I05a3a4835e225a1e413ec3540a7c7e4a2d477084
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

paths/paths_js.go

@@ -0,0 +1,9 @@
+// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package paths
+
+func ensureStateDirPerms(dirPath string) error {
+	return nil
+}