RFR: 8353572: x86: AMD platforms miss the check for CLWB feature flag

[Aleksey Shipilev]

On Wed, 2 Apr 2025 17:49:30 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Noticed this when doing [JDK-8353558](https://bugs.openjdk.org/browse/JDK-8353558). We only check for CLWB feature flag for Intel platforms. But AMD APM (Rev. 3.36—March 2024) tells me there is a CLWB flag in CPUID Fn0000_0007_EBX_x0 leaf as well. It is in the same place as the flag for Intel.
> 
> Additional testing:
>  - [x] Ad-hoc tests on Ryzen 5950X

@adinn, this is your code for JEP 352, originally. Simple omission? Or maybe AMD arch did not map this flag to any feature  back in the days? I think this is started with Family 17h or even Zen 2.

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PR Comment: https://git.openjdk.org/jdk/pull/24385#issuecomment-2773461404