Partial Backport of 'Add support for Apple silicon': Fix Big Sur detection
XCode's python returns 11.0 Homebrew's python returns 10.16
Fixes #311 (closed)
Partial backport of !661 (merged) for 1.18.2
XCode's python returns 11.0 Homebrew's python returns 10.16
Fixes #311 (closed)
Partial backport of !661 (merged) for 1.18.2