reflink: osx: check that not older than High Sierra
reflink: osx: check that not older than High Sierra

Signed-off-by: Ruslan Kuprieiev <e9bfb2c543dd33934bcff71879b108246996b567@iterative.ai>

dmpetrov/dataversioncontrol,dataversioncontrol/dvc,dataversioncontrol/dvc,efiop/dvc,efiop/dvc,dmpetrov/dataversioncontrol