[jdk8u] RFR: 8304143: Exclude duplicated class on linux, aix, and macos [v2]

[Severin Gehwolf]

On Tue, 14 Mar 2023 15:21:51 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

> We should only exclude the class on Linux. That's the OS where the `SystemMetrics` class is actually implemented. In order to solve the resulting build break on Mac and AIX, we should revert additions of the `null` returning classes there. Perhaps with #39.
> 
> I propose the following course of action to fix it:
> 
>     1. Only exclude `SystemMetrics.java` on Linux from the `solaris` directory in this PR. Make this PR dependent on #39 (dependent pull request).
>     2. Revert stub impl additions on Mac OS X and AIX with #39.

Change of plan. Do all of it here, and use JDK-8304053 as the bug to integrate.

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