When --app-image and --icon are both specified, jpackage creates a shortcut for the main launcher on Linux.

This is incorrect behavior; jpackage should not alter the provided app image. --icon parameter should be ignored, or jpackage should exit with an error. When the --app-image parameter is specified, the --icon parameter makes sense only for bundlers that can use it to configure the installer (e.g., exe). rpm and deb bundles don't have icons in the it configuration.

The AppImagePackageTest.testEmpty(true) test should be modified to fail if jpackage adds desktop files to rpm/deb bundle.