[jdk8u-dev] RFR: 8369226: GHA: Switch to MacOS 15

[Sergey Bylokhov]

On Thu, 8 Jan 2026 01:05:50 GMT, Andrew John Hughes <andrew at openjdk.org> wrote:

> This is a backport of [JDK-8369226](https://bugs.openjdk.org/browse/JDK-8369226) from 11u that upgrades from macos-13 to macos-15-intel, and XCode from 14.3.1 to 16.4, as MacOS 13 runners are now unavailable.
> 
> Due to the different structure of the GHA support in 8u, and the absence of aarch64 on MacOS, this is a backport in spirit rather than a 1:1 relationship, with the same values being changed in their different locations in the 8u `submit.yml`.

Marked as reviewed by serb (Reviewer).

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PR Review: https://git.openjdk.org/jdk8u-dev/pull/738#pullrequestreview-3675821777