[lworld] RFR: 8368475: [lworld] Add preview classes to jimage at make time [v2]

[David Beaumont]

On Tue, 23 Sep 2025 19:12:16 GMT, David Beaumont <duke at openjdk.org> wrote:

>> Copies valuetype classes for each module into corresponding "<module>/META-INF/preview/..." sub-directories to be pulled into jimage files and processed by the new preview mode handling code.
>> 
>> There might be a better way to do this in terms of Makefile semantics, but this seems to work well enough and doesn't prevent the value-class JAR files being generated for patching (which is still how everyone will get value classes until the rest of the work is plumbed in).
>> 
>> To enable the new preview mode work, set the "DISABLE_PREVIEW_PATCHING" system property to "true".
>> 
>> This PR is stacked on top of https://github.com/openjdk/valhalla/pull/1615 and only contains the single commit:
>> https://github.com/openjdk/valhalla/commit/d5941080fc1983fd436fc60962630f27b561a9b3
>
> David Beaumont has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains eight new commits since the last revision:
> 
>  - Copy value classes into preview directories for inclusion in jimage
>  - add system property guard to preview mode
>  - jimage writer changes to support preview mode.
>    
>    * Remove TODOs now jimage version is bumped
>    * jimage writer changes to support preview mode.
>  - Word smithing flags definitions.
>  - Add workaround until new image writing code is in
>  - Clarifying flag docs for /packages/xxx case
>  - Java ImageReader changes for preview mode
>  - C++ preparation for preview mode

Regenerating PR so it has a base branch to work from.

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PR Comment: https://git.openjdk.org/valhalla/pull/1616#issuecomment-3325272077