Changes are not reflected in Electron when using an external directory

* **Version**: 2.8.2

Sorry, that's already my second question.

Since I failed to use electron-webpack with Yarn Workspaces, I am using an external directory through an alias, like this:

```
resolve: {
alias: {
'@common': Path.resolve(__dirname, '../common')
}
}
```

It works, and when a change is made in the common directory, I can see that _something_ is being re-compiled by Electron:

```
[0] wait - compiling...
[0] event - compiled successfully
```

However, the Electron app itself is not refreshing, and if I force a refresh, the latest version of the app is not there. If I restart Electron completely, it works. Any idea what the problem could be?

Thanks a lot.

Reproduce the issue with the shown webpack resolve.alias mapping to an external ../common directory, then compare the successful compilation log with Electron's refresh behavior. Done means changes in the external directory are visible in the running app without restarting Electron or relying on a forced refresh.

Written by the indexing model from the issue text.