title: Ionic 3 change variable/theme in build time
body: <p>I need to create 2 themes in ionic 3.
  Actually I just need to have 2 versions of variables.scss file.</p>
  
  <p>One will have one pallets of color, another one the same variables but different colors.</p>
  
  <p>Is it possible to say ionic in build time which theme (variables.scss) to use, or somehow to change color pallet in build time ?</p>