buid(bin):binary for musl

[NewFuture]

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[Copilot]

Pull Request Overview

This PR adds support for producing a statically linked musl-based ddns binary, refines existing CI steps, and ensures the correct MutableMapping import on Python 2/3.

• Annotate Python version branches in util/cache.py.
• Update GitHub Actions: switch test -e to test -f for stricter file checks, and introduce a pack-musl job.
• Add an install script for patchelf and a multi-stage Dockerfile to build the musl binary.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
util/cache.py	Added inline comments to clarify Python 3 vs. Python 2 import paths.
.github/workflows/build.yml	Changed file-existence tests, removed ambiguity, and added pack-musl job.
.github/install-patchelf.sh	New script to fetch and install a specific patchelf release.
.build/musl.Dockerfile	New Dockerfile for building a static musl-linked binary via Nuitka.

Comments suppressed due to low confidence (2)

.build/musl.Dockerfile:10

• The fallback installs mix version 0.17.2.1 via pip while the install script targets 0.18.0—this version mismatch may lead to unexpected behavior. Align versions or centralize the version constant.

RUN apk add --update --no-cache patchelf\    || /tmp/install-patchelf.sh\    || pip3 install patchelf==0.17.2.1

.github/workflows/build.yml:290

• This run: step mixes a commented command at the same indentation, which likely breaks YAML parsing. Consider using a multiline literal (|) for the script block or removing the inline comment.

run: find output -mindepth 2 -type f -exec mv -t output {} +

[Copilot]

[nitpick] This run: step is duplicated across multiple jobs—consider extracting it into a reusable workflow step or using YAML anchors to reduce repetition.