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

[Julian Waters]

On Tue, 24 Sep 2024 12:56:10 GMT, George Adams <gdams at openjdk.org> wrote:

>> You can make it a link using markdown `[]()` syntax.
>
>> You can make it a link using markdown `[]()` syntax.
> 
> yeah I'll do that

I will approve once this is fixed, looks good

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PR Review Comment: https://git.openjdk.org/jdk/pull/21154#discussion_r1773297953