stdenvBootstrapTools: update aarch64 musl

[alyssais]

A couple of notes first:

• I'm not sure why Hydra doesn't show the build products on the build page. I found them by inspecting hydra-build-products in the output. But I don't see the build products on aarch64: update bootstrap-files #151399 's Hydra build either, so I guess this has just been broken forever and this is how everybody does it?
• AFAICT, this is our first time uploading musl tarballs to tarballs.nixos.org, so I had to choose where to put them. We weren't forward-thinking with including the libc in the names of the Glibc bootstrap tarballs, so I've just stuck a "-musl" suffix on the end, but we can change that if it would be better to use some other naming scheme.

---

The aarch64 musl bootstrap tools are woefully outdated. Just getting them to the point of being able to build new versions of themselves required a number of hacks that can be reverted once we have new bootstrap tools, and before that it stdenv didn't even build for the preceding three years.

So, following the script established by previous bootstrap tools updates:

Files came from this Hydra build:

https://hydra.nixos.org/build/246470544

…which used nixpkgs revision dd5621d to instantiate:

/nix/store/g480ass2vjmakaq03z7k2j95xnxh206a-stdenv-bootstrap-tools.drv

…and then built:

/nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools

I downloaded these files from Hydra and prefetched them into the Nix store with the following commands:

STOREPATH=95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools
OPTIONS="--option binary-caches https://cache.nixos.org --option trusted-public-keys cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
nix --extra-experimental-features nix-command store prefetch-file \
  file://$(nix --extra-experimental-features nix-command store add-file --name bootstrap-tools.tar.xz  $(nix-store ${OPTIONS} -r /nix/store/${STOREPATH})/on-server/bootstrap-tools.tar.xz)
nix --extra-experimental-features nix-command store prefetch-file --executable \
  file://$(nix --extra-experimental-features nix-command store add-path --name busybox $(nix-store ${OPTIONS} -r /nix/store/${STOREPATH})/on-server/busybox)

These commands produced the following output:

warning: you did not specify '--add-root'; the result might be removed by the garbage collector
Downloaded 'file:///nix/store/fm8ys5bb737j82xgyiciyzpcwmzyi9b2-bootstrap-tools.tar.xz' to '/nix/store/jml0gh0q2rnc9sgr87irz0jfbl0fq545-fm8ys5bb737j82xgyiciyzpcwmzyi9b2-bootstrap-tools.tar.xz' (hash 'sha256-ZY9IMOmx1VOn6uoFDpdJbTnPX59TEkrVCzWNtjQ8/QE=').
warning: you did not specify '--add-root'; the result might be removed by the garbage collector
Downloaded 'file:///nix/store/rn9fx55mw2s0qg90zdjxa9xn11nlmjpg-busybox' to '/nix/store/9qylz8gqll63pprwkwlyfs9g4zilak2m-rn9fx55mw2s0qg90zdjxa9xn11nlmjpg-busybox' (hash 'sha256-WuOaun7U5enbOy8SuuCo6G1fbGwsO16jhy/oM8K0lAs=').

I used the hashes from the output above to create the fetchurl invocation which is part of this commit.

I then started the bootstrap with the following command:

nix --extra-experimental-features nix-command build -L -f . --arg localSystem '(import ./lib).systems.examples.aarch64-multiplatform-musl' hello

As @lovesegfault requested, here are the the sha256sums of all the on-server components for extra verification:

sha256sum /nix/store/${STOREPATH}/on-server/*

…which produced the following output:

658f4830e9b1d553a7eaea050e97496d39cf5f9f53124ad50b358db6343cfd01  /nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools/on-server/bootstrap-tools.tar.xz
20cdfecb084ddb6b6b958f2b78fd2cc1d9641632f81ec7d5a48fae0a963ad0fa  /nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools/on-server/busybox

[lovesegfault]

I think this is as good a time as any to start using full triples for the bootstrap archive names. What do you think of http://tarballs.nixos.org/stdenv/aarch64-unknown-linux-musl/dd5621df6dcb90122b50da5ec31c411a0de3e538/?

[alyssais]

That sounds sensible to me if you're happy with it. I'll update the PR.

[lovesegfault]

Uploaded:

$ STOREPATH=95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools

$ sha256sum /nix/store/${STOREPATH}/on-server/*
658f4830e9b1d553a7eaea050e97496d39cf5f9f53124ad50b358db6343cfd01  /nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools/on-server/bootstrap-tools.tar.xz
20cdfecb084ddb6b6b958f2b78fd2cc1d9641632f81ec7d5a48fae0a963ad0fa  /nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools/on-server/busybox

$ aws s3 cp --recursive --acl public-read /nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools/on-server/ s3://nixpkgs-tarballs/stdenv/aarch64-unknown-linux-musl/dd5621df6dcb90122b50da5ec31c411a0de3e538/
upload: ../../../../nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools/on-server/busybox to s3://nixpkgs-tarballs/stdenv/aarch64-unknown-linux-musl/dd5621df6dcb90122b50da5ec31c411a0de3e538/busybox
upload: ../../../../nix/store/95lm0y33dayag4542s8bi83s31bw68dr-stdenv-bootstrap-tools/on-server/bootstrap-tools.tar.xz to s3://nixpkgs-tarballs/stdenv/aarch64-unknown-linux-musl/dd5621df6dcb90122b50da5ec31c411a0de3e538/bootstrap-tools.tar.xz

$ aws s3 cp --recursive s3://nixpkgs-tarballs/stdenv/aarch64-unknown-linux-musl/dd5621df6dcb90122b50da5ec31c411a0de3e538/ ./
download: s3://nixpkgs-tarballs/stdenv/aarch64-unknown-linux-musl/dd5621df6dcb90122b50da5ec31c411a0de3e538/busybox to ./busybox
download: s3://nixpkgs-tarballs/stdenv/aarch64-unknown-linux-musl/dd5621df6dcb90122b50da5ec31c411a0de3e538/bootstrap-tools.tar.xz to ./bootstrap-tools.tar.xz

$ sha256sum bootstrap-tools.tar.xz busybox
658f4830e9b1d553a7eaea050e97496d39cf5f9f53124ad50b358db6343cfd01  bootstrap-tools.tar.xz
20cdfecb084ddb6b6b958f2b78fd2cc1d9641632f81ec7d5a48fae0a963ad0fa  busybox