RFR: 8257620: Do not use objc_msgSend_stret to get macOS version

[Anton Kozlov]

On Wed, 2 Dec 2020 19:27:25 GMT, Phil Race <prr at openjdk.org> wrote:

>> Please review a small change that replaces use of objc_msgSend_stret in macOS platform code with pure ObjC code. It's also a prerequisite for macOS/AArch64 support, where objc_msgSend_stret is not available.
>
> Surely these days you can just call [NSProcessInfo operatingSystemVersion] directly ?
> If I read the doc below it is in the 10.10 SDK and later.
> https://developer.apple.com/documentation/foundation/nsprocessinfo/1410906-operatingsystemversion?language=occ

@prrace could you look at this?

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PR: https://git.openjdk.java.net/jdk/pull/1569