When i create angular-project(ng new projectname), it automatically build inline.bundle.js, main.bundle.js, polyfills.bundle.js, styles.bundle.js, vender.bundle.js in dist folder.
I can use the dist/index.js in backend.
So my question is "Ng4 build webpack automatically?"
When you use angular-cli to create an angular 2 project, the project is automatically build with webpack.
Angular-cli changed from systemjs to webpack a while ago.
If you want to get the webpack configuration file you can use ng eject.
https://github.com/angular/angular-cli/wiki/eject
Edit based on comment:
There is no dependency on webpack in your angular project because angular/cli has a dependency on webpack and will install webpack for you. If you check your node_modules folder, you will see that webpack is there.
from your project home directory, run the next command:
npm run build
this command will create a folder named dist.
in this folder you will find your files.
Edit the file webpack.config.js to change where the webpack places your files.