fix: Native AOT for linux-musl-arm64

[jpnurmi]

Publishing a minimal Alpine .NET AOT container on a Mac with Apple silicon requires linux-musl-arm64 as brought up in:

• Sentry 5.11 causes DllNotFoundException in Native AoT application #4296 (comment)

Problem: GitHub Actions hosted Node.js not available for MUSL ARM64

Node.js is required for JS actions, such as actions/checkout. For various reasons, GitHub Actions forces all containers to run a pre-compiled Node.js from the host, bind-mounted to the container in the /__e (aka. "externals") directory. The problem is that there's no suitable pre-compiled version for Linux MUSL ARM64.

A workaround is possible but it gets quite hacky. First of all, we need to bind-mount either /__e/node20 or /__e/node20/bin to "escape" the built-in /__e bind-mount. Secondly, we need to make sure /__e/node20/bin/node points to a working node executable. In our case, we link it to the system installation i.e. /usr/bin/node. Finally, we need to alter /etc/os-release and pretend not to be Alpine (change ID=alpine to anything else) to avoid the following hard-coded Alpine container compatibility check:

Error: JavaScript Actions in Alpine containers are only supported on x64 Linux runners. Detected ...

// Check for Alpine container compatibility
if (!Constants.Runner.PlatformArchitecture.Equals(Constants.Architecture.X64))
{
    var os = Constants.Runner.Platform.ToString();
    var arch = Constants.Runner.PlatformArchitecture.ToString();
    var msg = $"JavaScript Actions in Alpine containers are only supported on x64 Linux runners. Detected {os} {arch}";
    throw new NotSupportedException(msg);
}

https://github.com/actions/runner/blob/main/src/Runner.Worker/Handlers/StepHost.cs

See also:

• self-hosted: support Alpine actions/runner#801

[Flash0ver]

🤘 ... 2 questions and 1 nitpick