I have an a icon font that I want to use in my Sencha project, but I'm running into issues when trying to build for production.

The library that I'm using is called Material Design Icons. I downloaded the files and placed the folder (which I named material-design) in {project directory}/ext/packages/. This is the same directory where the font-awesome folder lives. I then modified the css configuration object in app.json to the following:

    "css": [
            // this entry uses an ant variable that is the calculated
            // value of the generated output css file for the app,
            // defined in .sencha/app/defaults.properties
            "path": "${build.out.css.path}",
            "bundle": true,
            "exclude": ["fashion"]
            // Note that the path can also be set to pull the font in from the materidesignicons server.
            // "path": "http://cdn.materialdesignicons.com/2.0.46/css/materialdesignicons.min.css",
            "path": "../ext/packages/material-design/css/materialdesignicons.min.css",
            "bundle": true
This works and I'm able to display icons from that library in my project while developing, however when I build the project, the files are not included.

Is there something that I need to do to ensure that these files are included in the build?