RFR: 8353009: Document target selection flag for Windows AArch64 builds [v3]

[Magnus Ihse Bursie]

On Mon, 31 Mar 2025 18:11:27 GMT, Saint Wesonga <duke at openjdk.org> wrote:

>> The target selection configuration flag for Windows AArch64 should be added to the build documentation for improved discoverability and completeness.
>
> Saint Wesonga has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add instructions for a native Windows AArch64 build

It might still make sense to document that to cross-compile to aarch64, the flag `--openjdk-target=aarch64-unknown-cygwin` should be used -- that is in no way obvious or trivial to figure out.

I think what you are talking about is the fact that, at least currently, the BuildTools distribution of Visual Studio do not include aarch64-hosted compilers, so to be able to run native builds without the Prism emulation, you need to install the full Visual Studio, including the IDE. This too might be worth documenting, with the caveat that it applies currently but might change in the future.

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PR Comment: https://git.openjdk.org/jdk/pull/24267#issuecomment-2778893458