[CMake] Tracking progress of CMake TAR

[Person Withhats]

When running tar via CMake (in order to use cross-platform work-ability and
what not) it'd be great to have a progress bar of any sort.

It's awkward to wait 30-60 minutes for file untarring with absolutely 0
information. I'm not aware of any way to do this through CMake directly,
only alternative is e.g. python script that does the untar for me.

Any suggestions? (sorry if this is reposted, can't remember if acc was
approved before or after sending one time)
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