Append linux to the Linux OMERO clients (rebased onto develop)


This is the same as gh-2591 but rebased onto develop.

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Fixes https://trac.openmicroscopy.org.uk/ome/ticket/12187

To test this PR, 
- check the Insight insight is now appended with `-linux`
- check the Insight clients package is appended with `.linux`
- check the clients for the other platforms are unaffected by these changes