RFR: 8361478: GHA: Use MSYS2 from GHA runners

[Aleksey Shipilev]

On Tue, 8 Jul 2025 11:35:26 GMT, Julian Waters <jwaters at openjdk.org> wrote:

> I recall there were some issues with using MSYS2 that comes with Actions. That was a long time ago though, are they no longer a problem with current Actions and MSYS2 versions?

We used to have a problem building jtreg, so we pinned and later unpinned the version: [JDK-8310259](https://bugs.openjdk.org/browse/JDK-8310259). But today, we do not build jtreg on Windows at all. And we have not seen any issues with MSYS2 since. So I think it is okay to bump the version now. We can retract it back if we find problems, it would only require rewiring the `PATH` a bit awkwardly.

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PR Comment: https://git.openjdk.org/jdk/pull/26156#issuecomment-3048827047