disable mixins

Author: gossi

lib/clark-plugin.js

@@ -45,7 +45,9 @@ module.exports = class ClarkPlugin extends Plugin {
       // @if, @else and @else if
       // Iterate over numeric ranges with @for
       // Iterate over lists with @each
-      require('postcss-advanced-variables'),
+      require('postcss-advanced-variables', {
+        disable: '@mixin, @include, @content'
+      }),
 
       // https://github.com/jonathantneal/postcss-short
       // Shorthand properties