title: avoid @import being included twice - rails engine
body: <p>i have a rails engine which is being consumed by an application. The engine and the application both are dependent on a mixin file so both of them does</p>
  
  <p>@import 'mixins'</p>
  
  <p>But on css compression these mixins will be included twice.</p>
  
  <p>Is there anyway to avoid this duplication.</p>