RFR: 8303485: Replacing os.name for operating system customization

[Roger Riggs]

On Wed, 8 Mar 2023 19:15:16 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

> Improvements to support OS specific customization for JDK internal use:
>  - To select values and code; allowing elimination of unused code and values
>  - Optionally evaluated by build processes, compilation, or archiving (i.e. CDS)
>  - Simple API to replace adhoc comparisons with `os.name`
>  - Clear and consistent use across build, runtime, and JDK modules
>  
> The PR includes updates within java.base to use the new API.

To see the knock-on effects of using the API in other modules, see the Draft PR #12961

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PR: https://git.openjdk.org/jdk/pull/12931