Is there any way to merge SCSS and CSS?

Currently I do it as follows but it doesn't work. The code below supposed to compile scss into a temp directory and then merge it with the plain css.

```
mix.sass('resources/assets/sass/app.scss', '../resources/assets/tmp_compilation_files/scss-assets.css').styles([ 'resources/assets/tmp_compilation_files/scss-assets.css', 'node_modules/isteven-angular-multiselect/isteven-multi-select.css' ], 'public/css/app.css');

```

but nothing. The compiled SASS is missing in the public/css/app.css file. This is so annoying, such a simple task and it's not doable. I was able to do it with elixir - compiling scss into a tmp directory (./resources/tmp) and then merging it with the css files using styles().

I also haven't found any info in the documentation about the path params - where I specify absolute paths, where relative to the public directory?