RFR: JDK-8260518: Change default -mmacosx-version-min to 10.12

[Phil Race]

On Wed, 27 Jan 2021 19:23:48 GMT, Erik Joelsson <erikj at openjdk.org> wrote:

> To guarantee backwards compatible binaries on Macos, we use the option -mmacosx-version-min. This is currently set to 10.9, which is a really ancient version. I propose we bump this to 10.12, which is still a rather conservative old version (support ended in 2019).
> 
> The driving issue for bumping this now is the aarch64 port, where building for aarch64 requires the version min to be set to 11.0. Having a large gap between the target versions becomes problematic as we hit a lot of deprecation warnings in shared code. To be able to fix these deprecation warnings, we need a smaller version gap.
> 
> Just bumping us to 10.12 triggers warnings in libsplashscreen, so I will temporarily add "deprecated-declarations" to the list of disabled warnings there until they can be fixed in JDK-8260402.

Marked as reviewed by prr (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/2268