Today we got this error when uploading our IPA generated with VoltBuilder to Apple Store via Application Loader:
ERROR ITMS-90596: "Invalid Bundle. The asset catalog at 'Payload/La Riserva di Caccia.app/Assets.car' can't be processed. Rebuild your app, and all included extensions and frameworks, with the latest GM version of Xcode and resubmit."
Oops - I should have paid more attention to your initial posting. The Application Loader is no longer supported by Apple. You should use Apple’s Transporter app (available in the App Store) instead.
Another option is to let VoltBuilder do the upload for you, as part of the build. That way, you won’t need a Mac.