RFR: 8342578: GHA: RISC-V: Bootstrap using Debian snapshot is still failing [v2]

[Fei Yang]

> In JDK-8339548, we switched to use Debian snapshot (https://snapshot.debian.org/archive/debian/20240228T034848Z/) for bootstrap. The reason is that we don't have a stable Debian release for RISC-V yet and Debian "sid" (https://httpredir.debian.org/debian) that we use for debootstrapping RISC-V breaks at that time. This works as expected for about one month. But bad news is that GHA linux-cross-build job for RISC-V starts to fail again this week. Sigh! I guess there might be some change on the distro running on GHA test machines as same debootstrap command still works on my x64 machine running Ubuntu 22.04.5.
> 
> Good news is that that Debian "sid" can now bootstrap for RISC-V. So this simply switches back to Debian "sid". As the version
> of dpkg command on GHA machines is old (1.21.1), we need to add one extra option `--no-merged-usr` for bootstrap command to work (More discussion here: https://bugs.launchpad.net/ubuntu/+source/base-files/+bug/2054925). This option seems not necessary for newer dpkg versions like 1.22.6.
> 
> Testing:
> - [x] GHA test

Fei Yang has updated the pull request incrementally with one additional commit since the last revision:

  Comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21575/files
  - new: https://git.openjdk.org/jdk/pull/21575/files/24cd3a93..5d02c1c2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21575&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21575&range=00-01

  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21575.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21575/head:pull/21575

PR: https://git.openjdk.org/jdk/pull/21575