[jdk21u-dev] RFR: 8339548: GHA: RISC-V: Use Debian snapshot archive for bootstrap

[Fei Yang]

Hi all,

This pull request contains a backport of commit [9e0ccb8b](https://github.com/openjdk/jdk/commit/9e0ccb8bbd01ffbac466288977a770dd09e357af) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Fei Yang on 6 Sep 2024 and was reviewed by Aleksey Shipilev and Erik Joelsson.

Thanks!

Testing:
- [x] GHA linux-cross-build job

-------------

Commit messages:
 - Backport 9e0ccb8bbd01ffbac466288977a770dd09e357af

Changes: https://git.openjdk.org/jdk21u-dev/pull/962/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=962&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339548
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/962.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/962/head:pull/962

PR: https://git.openjdk.org/jdk21u-dev/pull/962