PostCSS build fails on Windows

[richiksc]

Debug info OS: Windows 10 v1809. Node: v12.1.0 Browser: Chrome 74 Stable

Describe the bug The command npm run build logs a ENOENT error from PostCSS requiring utils.css due to the file path starting with a double C:\C:\ (it should start with a single C:\). Styles from utils.css are not loaded in the built page and some components are left unstyled (such as the buttons).

To Reproduce Steps to reproduce the behavior:

1. Clone the project on a Windows machine. I am using the Git Bash shell, however, so Linux tools are available.
2. npm install
3. npm run build

4. The following error is logged:

   [Error: ENOENT: no such file or directory, open 'C:\C:\Users\<user>\code\proxx\src\services\preact-canvas\utils.css'] {
     errno: -4058,
     code: 'ENOENT',
     syscall: 'open',
     path: 'C:\\C:\\Users\\<user>\\code\\proxx\\src\\services\\preact-canvas\\utils.css'
   }

   This error occurs due to the double C:\C:\ at the beginning of the path. I can't seem to figure out why it does that, and I couldn't trace it to a rollup plugin, so I'm opening the issue here. Has the project been tested to build on Windows at all?

5. npm run serve
6. Open localhost:8080 in browser (in my case, Chrome 74) and observe the page. Styles from utils.css are not loaded.

Expected behavior PostCSS builds sucessfully and styles from utils.css are loaded.