What determines the value of DEBUG?

[JHKennedy4]

I recently experienced an outage in production caused by DEBUG resolving to true (see: ember-app-scheduler/ember-app-scheduler#69). I'd like to get a better idea of how this value is getting set so we can fix our build appropriately.

Thanks in advance.

[blimmer]

Did you figure this out? I'm trying to figure this out, too.