RFR: 8372393: Document requirement for separate metallib installation with Xcode 26.1.1

[Erik Joelsson]

On Tue, 25 Nov 2025 11:25:59 GMT, Galder Zamarreño <galder at openjdk.org> wrote:

> Document the metal toolchain requirements starting with Xcode 26.

doc/building.html line 547:

> 545: comes bundled with Xcode, so it needs to be installed separately. This can
> 546: either be done via the Xcode's Settings/Components UI, or in the command line
> 547: calling <code>xcodebuild -downloadComponent metalToolchain</code>.</p>

When I checkout this branch and run `make update-build-docs`, the line breaks here are done differently. It would be good to not introduce future diffs when the html files are regenerated next time.

Suggestion:

<p>Starting with Xcode 26, introduced in macOS 26, the Metal toolchain
no longer comes bundled with Xcode, so it needs to be installed
separately. This can either be done via the Xcode's Settings/Components
UI, or in the command line calling
<code>xcodebuild -downloadComponent metalToolchain</code>.</p>

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PR Review Comment: https://git.openjdk.org/jdk/pull/28489#discussion_r2560088391