release: bump required osx version to 10.8. Credit jonasschnelli.
release: bump required osx version to 10.8. Credit jonasschnelli.

libc++ on 10.7 causes too many issues.

See #8577 for discussion/details.

Github-Pull: #9015
Rebased-From: 339c4b6c3a8e68e4bba1969d144e413a462b68f1

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