feat: add multi-engine regex flavour support

scripts/install-cpp-engine.mjs

@@ -0,0 +1,14 @@
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+import { installCppPack } from "./cpp-engine-pack.mjs";
+
+const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+const arguments_ = process.argv.slice(2);
+if (arguments_.length > 1) {
+  throw new Error(
+    "Usage: node scripts/install-cpp-engine.mjs [.engine-build/cpp]",
+  );
+}
+const source = path.resolve(root, arguments_[0] ?? ".engine-build/cpp");
+const result = await installCppPack(source, root);
+console.log(`Installed verified C++ engine pack at ${result.output}.`);