mkdirs return value is ignored

### Affected version

HEAD

### Bug description

There is a lot of code scattered throughout the project where we do things like

metainfDir.mkdirs();

without checking if the operation succeeded. Depending on context this can result in a harder to diagnose exception further down the line, or a war file that is simply missing things it should have. Either way we should check the results of these operations and throw the available mojo exception earlier.