Refactor OS::Mac::Version.

[reitermarkus]

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Closes Homebrew/homebrew-cask#90326.

[maraflush]

Hello your refactoring not working properly here. Since a week, homebrew seems work only with bottle but it not able to trigger the compiler like gcc or llvm. Just before to trigger gcc, the following exception is raised : "Array into Integer conversion", here @koenvd's fix seems not work.
Could you fix it, please.
Best regards,