RFR: JDK-8260518: Change default -mmacosx-version-min to 10.12 [v2]

[Erik Joelsson]

> 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.

Erik Joelsson has updated the pull request incrementally with one additional commit since the last revision:

  Copyright year

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2268/files
  - new: https://git.openjdk.java.net/jdk/pull/2268/files/41d60207..4eb09479

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2268&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2268&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2268.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2268/head:pull/2268

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