prepend portion of asset-urls not accounted for

[runspired]

Related ember-cli/ember-cli-terser#275 (comment)

When specifying

new EmberApp(defaults, {
  fingerprint: {
    prepend: '<<CDN URL>>'
  }
})

It appears to be impossible to build with ember-cli-terser enabled at all, even when deactivating sourcemaps via

new EmberApp(defaults, {
  sourcemaps: {
    enabled: false
  }
})

Just in case ember-cli-terser and broccoli-terser-sourcemap need to be aware of this URL I added the publicUrl option

new EmberApp(defaults, {
  'ember-cli-terser': {
    publicUrl: '<<CDN URL>>'
  },
  fingerprint: {
    enabled: false,
    publicUrl: '<<CDN URL>>'
  }
})

All of this was to no avail. Even with sourcemaps disabled I get logs like the following:

[WARN] (broccoli-terser-sourcemap) "<<CDN URL>>/assets/leaflet/leaflet-src-18322c41aab5808cecb4784380d74637.js.map" referenced in "assets/leaflet/leaflet-src-18322c41aab5808cecb4784380d74637.js" could not be found

As well as a build error:

Unexpected token punc «:», expected punc «,»

Using a debugger I find that this error is from within a sourcemap being parsed (surprising with them disabled?!)