The directory output for the fastqc tasks is causing issues on the
shared file system of the cluster, since it cannot properly determine
the age of the folder. As a result, it re-runs the fastqc tasks every
time a workflow is restarted, regardless of whether the task has already
completed.

To prevent this, a single dummy output file '.done' has been added to
the fastqc tasks which will be written when fastqc exits successfully.