[jdk8u] RFR: 8304053: Revert os specific stubs for SystemMetrics [v4]

[Andrew John Hughes]

On Tue, 14 Mar 2023 16:27:08 GMT, Adam Farley <afarley at openjdk.org> wrote:

>> This change excludes the duplicated class SystemMetrics, and ensures we use the platform-specific version of the SystemMetrics class instead.
>
> Adam Farley has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Adding comment
>   
>   Signed-off-by: Adam Farley <adfarley at redhat.com>

FYI: Linux builds are broken without this too:

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PR: https://git.openjdk.org/jdk8u/pull/40