build: OMERO.cpp zips are versioned with platform information

Intended to allow Jenkins jobs or end users to override the Ant os.name, os.version and os.arch properties with a single "platform" property which encodes the OS description in a unique and meaningful manner.

--no-rebase

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Testing

- jobs will remain green
- OMERO.cpp zips will gain a version number and retain the existing os name/arch/version suffix.