8369226: GHA: Switch to MacOS 15

[shipilev]

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Making GHA more stable.

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Progress

• [x] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue
• [ ] JDK-8369226 needs maintainer approval

Issue

• JDK-8369226: GHA: Switch to MacOS 15 (Enhancement - P4)

Reviewers

• Martin Doerr (@TheRealMDoerr - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk17u-dev.git pull/4115/head:pull/4115
$ git checkout pull/4115

Update a local copy of the PR:
$ git checkout pull/4115
$ git pull https://git.openjdk.org/jdk17u-dev.git pull/4115/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 4115

View PR using the GUI difftool:
$ git pr show -t 4115

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk17u-dev/pull/4115.diff

Using Webrev

Link to Webrev Comment