By default, in CI environments, Ember CLI does not output anything between "building..." and "cleaning up". Depending on configuration and hardware, Discourse asset builds can take upwards of 60s, and so this lack of output can make the build feel 'stuck'.
This commit introduces an addon which checks for CI mode, and then outputs status information periodically. The logic is very similar to Ember CLI's non-CI progress output implementation (https://github.com/ember-cli/ember-cli/blob/04a38fda2c/lib/models/builder.js#L183-L185).
David Taylor