RFR: 8327493: Update minimum Xcode version in docs

Tue Mar 26 09:38:27 UTC 2024

On Tue, 26 Mar 2024 09:19:19 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> The file building.{md,html} indicates the required minimum version of Xcode to use. When the required minimum version of Clang was updated to 13 ([JDK-8325878](https://bugs.openjdk.org/browse/JDK-8325878)), the minimum Xcode version was not updated. It should now be Xcode 13.0, rather than 8.

Marked as reviewed by clanger (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/18483#pullrequestreview-1959819155