Merge js files into one with phpStorm

Using phpStorm, I would like to merge multiple javascript files into one. I installed the closure compiler and configured the file watcher to minify each javascript file.

Now, I would like to combine all of my javascript files into one.

Here's the architecture of my project (a test project to merge js files) :

index.php
js(folder) > first.js (+first.min.js), second.js(+second.min.js), third.js(+third.min.js)
cache (folder)

I would also like to merge (first.min.js, second.min.js, third.min.js) into folder cache > main.js.

Ideally, merging all of the files would happen automatically; I don't want to specify each js file manually.

Can someone explain the arguments I must use to configure my filewatcher?