docs(library-mode): add advanced usage warning (#14168)

guide/build.md

@@ -214,14 +214,18 @@ Or, if exposing multiple entry points:
 }
 ```
 
-::: tip Note
+::: tip File Extensions
 If the `package.json` does not contain `"type": "module"`, Vite will generate different file extensions for Node.js compatibility. `.js` will become `.mjs` and `.cjs` will become `.js`.
 :::
 
 ::: tip Environment Variables
 In library mode, all `import.meta.env.*` usage are statically replaced when building for production. However, `process.env.*` usage are not, so that consumers of your library can dynamically change it. If this is undesirable, you can use `define: { 'process.env.NODE_ENV': '"production"' }` for example to statically replace them.
 :::
 
+::: warning Advanced Usage
+Library mode includes a simple and opinionated configuration for browser-oriented and JS framework libraries. If you are building non-browser libraries, or require advanced build flows, you can use [Rollup](https://rollupjs.org) or [esbuild](https://esbuild.github.io) directly.
+:::
+
 ## Advanced Base Options
 
 ::: warning