RFR: 8363965: GHA: Switch cross-compiling sysroots to Debian bookworm

[Christoph Langer]

On Wed, 23 Jul 2025 16:20:52 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> I have noticed that GHA jobs started to fail when creating ppc64el sysroot. We are using Debian bullseye as the base for sysroots. Debian bullseye is LTS release. Perhaps counter-intuitively, LTS platform support shrinks over the LTS lifetime. Debian wiki: https://wiki.debian.org/LTS/Using -- says:
> 
> "Important: The current LTS version is Debian 11 ("bullseye") and will be supported until August 31st, 2026. Supported architectures in Debian 11 LTS are limited to amd64, i386, arm64 and armhf. Users of other architectures are especially encouraged to upgrade to Debian 12 (''bookworm''). "
> 
> We should consider switching to Debian bookworm for GHA cross-compiling sysroots. Again, Debian wiki: https://wiki.debian.org/DebianBookworm#Architectures -- says all architectures we need are supported. But actually, RISC-V is still only supported with sid. So, we need to be switching only current bullseye to bookworm, leaving sid as sid. This should change as Debian trixie releases in a few weeks, but we cannot wait for this long. Debian trixie update would be handled in [JDK-8363966](https://bugs.openjdk.org/browse/JDK-8363966).
> 
> Additional testing:
>  - [x] GHA cross-compilation jobs

Makes sense in order to keep all platforms active.

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Marked as reviewed by clanger (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26447#pullrequestreview-3050692591