Problem with directory junction in windows 10 (alias path in webpack)

## Description

While trying to create basic build on freshly installed gridsome, I found out that it has problems with directory junctions in Windows machines.

My local web server, where I keep everything for web development and non-php related projects, is in
` e:/xampp/htdocs/` which was mapped to directory junction to `e:/webroot/`.


### Steps to reproduce
Create directory junction in windows with `mklink` command. CD into that junction folder, create new project with gridsome and run development server.

### Expected result

Basic demo should be compiled without problems.

### Actual result

Error with g-image

```
Failed to render /
TypeError: Cannot read property 'width' of undefined
at render (e:/xampp/htdocs/test/gridtest/node_modules/gridsome/app/components/Image.js:38:27)
at e:\xampp\htdocs\test\gridtest\node_modules\vue\dist\vue.runtime.common.prod.js:6:22087
at Ie (e:\xampp\htdocs\test\gridtest\node_modules\vue\dist\vue.runtime.common.prod.js:6:22269)
at e:\xampp\htdocs\test\gridtest\node_modules\vue\dist\vue.runtime.common.prod.js:6:23399
at Le (e:\xampp\htdocs\test\gridtest\node_modules\vue\dist\vue.runtime.common.prod.js:6:23750)
at e._c (e:\xampp\htdocs\test\gridtest\node_modules\vue\dist\vue.runtime.common.prod.js:6:31905)
at a.render (e:/xampp/htdocs/test/gridtest/src/pages/Index.vue?25ed:1:89)
at a.t._render (e:\xampp\htdocs\test\gridtest\node_modules\vue\dist\vue.runtime.common.prod.js:6:34798)
at e:\xampp\htdocs\test\gridtest\node_modules\vue-server-renderer\build.prod.js:1:69946
at Zi (e:\xampp\htdocs\test\gridtest\node_modules\vue-server-renderer\build.prod.js:1:66510)
```