RFR: 8357119: Make Zero the default and only variant of HotSpot for iOS [v3]

[Magnus Ihse Bursie]

On Mon, 19 May 2025 05:14:27 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 two additional commits since the last revision:
> 
>  - Allow other JVMs again in hotspot.m4
>  - Improve README.md

README.md line 49:

> 47: If you need to tell configure the path of your boot JDK, or if configure fails with an error saying
> 48: it can't find a boot JDK, for instance if you downloaded a JDK in compressed archive form rather
> 49: than with an installer, you can pass `--with-boot-jdk=<java-directory-path>` to configure:

Suggestion:

than with an installer, you can pass `--with-boot-jdk=<java-directory-path>` to configure.

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PR Review Comment: https://git.openjdk.org/mobile/pull/35#discussion_r2097892763