RFR: 8357119: Make Zero the default and only variant of HotSpot for iOS [v2]

[Johan Vos]

On Fri, 16 May 2025 08:58:37 GMT, Julian Waters <jwaters at openjdk.org> wrote:

>> Currently, the Zero variant of HotSpot must be manually selected for mobile to compile properly for iOS, since iOS does not allow writeable and executable sections. Since Zero is, to my knowledge, the only valid HotSpot variant for iOS, this default should be handled by the build rather than require the developer to have specific knowledge about iOS and the mobile fork. I also took the opportunity to explicitly disallow selecting other JVM variants at all for iOS, this can be rolled back if my assumption turns out to be incorrect. While here, also touch up the build docs a little.
>
> Julian Waters has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Touch up README.md

@TheShermanTanker thank you for the PR. Looks good, some minor comments.
The biggest minor comment is probably about restricting the VM variant to Zero for all iOS builds. I believe there is value in building the server variant for the iOS simulator. While you can't distribute apps with it, it might help developers testing their apps quickly.

README.md line 48:

> 46: 
> 47: If you need to tell configure the path of the boot JDK, or if configure fails with an error saying
> 48: it can't find the boot JDK, for instance if you downloaded a JDK in compressed archive form rather

minor: change "the boot JDK" to "a boot JDK"

-------------

PR Comment: https://git.openjdk.org/mobile/pull/35#issuecomment-2886665175
PR Review Comment: https://git.openjdk.org/mobile/pull/35#discussion_r2093005460