all: adjust some build tags for wasi

A start.

Updates #8320

Change-Id: I64057f977be51ba63ce635c56d67de7ecec415d1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

paths/paths_wasm.go

@@ -0,0 +1,10 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package paths
+
+func ensureStateDirPerms(dirPath string) error {
+	return nil
+}
+
+func LegacyStateFilePath() string { return "" }