How to set different Compass configuration options for environments in Broccoli?

I'm currently using the ember-cli-broccoli-compass plugin for compiling my SASS. However I'm having trouble being able to assign the HTTP path for image assets in the stylesheets for different environments. This is what I have so far:

var EmberApp = require('ember-cli/lib/broccoli/ember-app');

var app = new EmberApp(
{
    compassOptions: 
    {
        httpPath: 'http://ift.tt/1cl344C',
        generatedImagesPath: 'http://ift.tt/1cl344C'
    }
});

When building the application for production (ember build -prod), it prepends the correct S3 path for the image assets in the stylesheets. However when running the application with ember server --proxy http://localhost:3000 the assets are built using the S3 path and not the local desired path of http://localhost:4200

How do I have environment specific Compass options for the httpPath when building image asset paths?