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

[Aleksey Shipilev]

On Fri, 18 Oct 2024 01:33:18 GMT, Fei Yang <fyang at openjdk.org> wrote:

> 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.
> 
> 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

.github/workflows/build-cross-compile.yml line 134:

> 132:         run: >
> 133:           sudo debootstrap
> 134:           --no-merged-usr

I have a question about this. https://wiki.debian.org/UsrMerge says: "This page tracks Debian support for the merged /usr directories scheme, i.e. the /{bin,sbin,lib}/ directories becoming symbolic links to /usr/{bin,sbin,lib}/." 

So turning this off gets us separate `/{bin,sbin,lib}/`, right? We clean up the unnecessary files from a sysroot in the next step, would that step miss `/{bin,sbin}` and subdirs in `/{lib}` then?

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PR Review Comment: https://git.openjdk.org/jdk/pull/21575#discussion_r1806568672