RFR: 8351851: Update PmemTest to run on AMD64

[Andrew Dinn]

On Thu, 3 Apr 2025 14:48:41 GMT, Ivan Šipka <isipka at openjdk.org> wrote:

> Remove default OS platform linux x86_64, remove @ignores allowing amd64 as a viable OS platform selection

I'm not sure if this change is correct. The original directive was ignored and replaced with an x86_64-only directive because of automated testing concerns documented in [PR 12352](https://github.com/openjdk/jdk/pull/12352). If this change is happening because those automated test restrictions no longer apply for all three of amd64 (by  which I mean not intel x86_64) aarch64 and ppc then reverting to the ignored directive would be fine. If the only change is that automated testing on amd64 now works as well as x86_64 then I would recommend modifying the first directive and keeping the ignored directive as the latter helps to clarify to general users how non-automated testing can be performed on aarch64 and ppc.

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PR Review: https://git.openjdk.org/jdk/pull/24416#pullrequestreview-2768213569