RFR: 8343190: GHA: Try building JTReg several times

[Erik Joelsson]

On Tue, 29 Oct 2024 10:58:34 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> We still sometimes have problems checking out JTReg build dependencies. [JDK-8342988](https://bugs.openjdk.org/browse/JDK-8342988) makes it less pronounced, but it still happens. We might need to do a retries for JTReg builds to make them more reliable.
> 
> Additional testing:
>  - [x] GHA (seeing retries with deliberately broken JTReg build)
>  - [x] GHA (passing JTReg build)

Marked as reviewed by erikj (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/21758#pullrequestreview-2401793625