Reapply 'Implement target_clones multiversioning'

See discussion in D51650, this change was a little aggressive in an
error while doing a 'while we were here', so this removes that error
condition, as it is apparently useful.

This reverts commit bb4934601d731465e01e2e22c80ce2dbe687d73f.

GitOrigin-RevId: fc53eb69c26cdd7efa6b629c187d04326f0448ca
18 files changed