Generate sass/css doesn't use hash filenames

[tnguyen-advicetrade]

When setting the resource root

i.e.
mix.setResourceRoot('public/assets');

The generate scss files do not use the hash for a respective image file.

The generated image filename:
2ndpg-hdr.0153009dd5cf3cc09e63.jpg

The resulting css style:
.someDiv { background-image: url(/public/assets/2ndpg-hdr.jpg?09845228d6032d2361194d24968b0c5c); }

As a result, images aren't displayed correctly