added os_version to unix build macro

[shimwell]

This PR into a feature branch is one option for getting os_version from the github action into the unix_share_build script as suggested in the review for #115

The only down side I can see with this approach is that the unix_share_build script currently makes use of lsb_release to find the Linux version. So perhaps this should also be removed?

[gonuke]

This seems like a good plan to me - just one suggestion for an improvement of an inherited issue...

[gonuke]

I think it makes sense to rely on the OS_VERSION variable instead of the lsb_release command, but I wonder how we avoid an inconsistency?

[shimwell]

I think it makes sense to rely on the OS_VERSION variable instead of the lsb_release command, but I wonder how we avoid an inconsistency?

We could use lsb_release to check the user specified / github action specified argument. If there is disagreement then the script could raise an error

I was also half thinking of having os_minor_version and os_major_version in the github action but that can wait for iteration 2 :-)

[shimwell]

Looks like we have settled on an option for this, so I shall merge it into the other feature branch so that the CI can be triggered