RFR: 8318692: Add instructions for creating Ubuntu-based sysroot for cross compilation [v2]

[Zixian Cai]

On Tue, 24 Oct 2023 02:22:39 GMT, Zixian Cai <zcai at openjdk.org> wrote:

>> Sometimes it's useful to have a Ubuntu-based chroot when you want to ensure compatibility of your deployment target and/or have access to packages that might not be in Debian upstream for some architectures.
>> 
>> Ubuntu-based sysroot warrants a separate instruction because `symlinks` is in the `universe` repository, and without that, `debootstrap` might fail with package not found, but it's not immediately obvious why.
>> 
>> This should be merged after #16332 for consistent formatting. Once #16332 is merged, I will update this PR.
>
> Zixian Cai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update rendered HTML

This is updated to follow the same formatting per #16332

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PR Comment: https://git.openjdk.org/jdk/pull/16331#issuecomment-1777159056