MGC Protection against multiple generate calls

In some cases, it's necessary to call the generate function multiple times from the same process (or at least it's allowed to do so, in principle). With our reproducer-script setup, the data cards are backed up before generation begins. We get a name conflict if this is done multiple times, which can cause the job to crash. This avoids the problem by including multiple backups of the cards (one per call to generate), which should be even more reliable in reproducing jobs.