feat: Node.js Alpine arm64 Unofficial Builds

[nschonni]

Description

Fixes#2475

Motivation and Context

I'm not sure if this actually is better than dropping the unofficial builds for all the Alpine builds, but opening as a draft.

Testing Details

I have no ARM64 devices to try the compilation on

Example Output(if appropriate)

Types of changes

• Documentation
• Version change (Update, remove or add more Node.js versions)
• Variant change (Update, remove or add more variants, or versions of variants)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other (none of the above)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• All new and existing tests passed.

[nschonni]

@MikeMcC399 thanks for pointing that out. I'm just trying to see if I can get the matrix to run/generate on x64/ARM for now

[nschonni]

Flipped out of review, as I figured out how to get the generated matrix to run on both x64 and ARM64 ubuntu for our smoke testing. Might be a concern around increasing the matrix size, but the jobs aren't particularly long

[nschonni]

If I want to use this, I'll need to rebase and include the 26 parts

[MikeMcC399]

This probably also has implications for the update readiness checks, since non-security releases should only proceed if musl builds for both amd64 & arm64 are available.

[nschonni]

I'll need to rebase again later, can't do it from the web

[MikeMcC399]

Having to wait for the arm64 musl build to complete every time looks like it could put additional hours on to the processing of a version update, delaying also Debian readiness, unless unofficial builds gets supercharged!

[MikeMcC399]

It seems likely that future node Docker Alpine Linux/amd64 image builds could transition to using musl builds published to https://nodejs.org/download/release/ if the approved PR nodejs/node#63737 to promote Alpine/x64 to Tier 2 is merged. Preparation for this is an open action item (see also Build WG minutes https://hackmd.io/@openjs-nodejs/BJNLz8jfGg 2026-07-02).

In that case this PR would cause an exception by retaining a dependency on https://unofficial-builds.nodejs.org. for node Docker Alpine Linux/arm64 image builds, whilst building Linux/s390x from source.

I suggest not to pursue the change proposed in this PR, and instead plan to use the official build for Linux/amd64 and build other architectures from source. Otherwise it would get overly complicated and it would delay security releases, which would need to wait, just because of using unofficial-builds for Linux/arm64.

[nschonni]

Closing this. I think it's better to rely on the Official releases going forward, and whether we still get the ARM builds included on the docker hub can be a separate discussion