Explain resume ability if unarchiving fails during installation

[interstateone]

xcodes can resume installation using a downloaded xip if it finds it in the expected location (its application support directory) when you run the install command. This is useful when unarchiving failed during the first run, often because of a lack of disk space. xcodes should explain this when unarchiving fails so that users know to re-run the same command instead of manually unarchiving the xip file.