Add prefix to zip file produced by dist-bftools target (rebased onto develop)



This is the same as gh-1134 but rebased onto develop.

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See https://trac.openmicroscopy.org.uk/ome/ticket/12327

To test this PR, download the `bftools.zip` artifacts produced by the daily job and unzip it locally. The content of the zip should be unzipped within a folder called `bftools`.