RFR: 8340804: doc/building.md update Xcode instructions to note that full install is required

[George Adams]

On Tue, 24 Sep 2024 12:55:17 GMT, Erik Joelsson <erikj at openjdk.org> wrote:

> You can make it a link using markdown `[]()` syntax.

yeah I'll do that

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PR Review Comment: https://git.openjdk.org/jdk/pull/21154#discussion_r1773293082