RFR: 8313701: GHA: RISC-V should use the official repository for bootstrap

[Fei Yang]

On Fri, 4 Aug 2023 09:18:11 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> RISC-V is now the [official Debian architecture](https://lists.debian.org/debian-riscv/2023/07/msg00053.html). This means that the official repository is slowly building up the package set, while the old debian-ports repo is [slowly rotting](https://lists.debian.org/debian-riscv/2023/08/msg00007.html). For futureproof-ness, we want to bootstrap from the official repo going forward.
> 
> Additional testing:
>  - [x] GHA

That sounds great to me. Thanks.

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Marked as reviewed by fyang (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/15149#pullrequestreview-1563789084