ci: cross-compile aarch64-apple-darwin from Linux (drop macos-latest lane)

[zackees]

Summary

Replaces the macos-latest runner for the aarch64-apple-darwin release lane with the existing ubuntu-latest runner already shared by every other target. Uses soldr + cargo-zigbuild + soldr's managed Apple SDK to produce real Mach-O arm64 binaries from Linux x86_64. Removes the last cross-platform-runner dependency from the release matrix.

What landed

• .github/workflows/release-auto.yml — aarch64-apple-darwin lane swaps to ubuntu-latest + new mac_cross_linux: true flag
• .github/workflows/template_native_build.yml — adds the mac_cross_linux boolean + matching build / PyO3 / staging / strip branches
• ci/docker-mac-arm64-cross/ — minimal ubuntu:24.04-based docker image + build.sh that reproduces the GHA flow locally and asserts via file(1) that all three artifacts are valid Mach-O arm64. The "NO CHEATING" local-validation gate.

How it was validated

Local docker run against current main:

staging/fbuild: Mach-O 64-bit arm64 executable
staging/fbuild-daemon: Mach-O 64-bit arm64 executable
staging/_native.abi3.so: Mach-O 64-bit arm64 dynamically linked shared library

Sizes: 23 MB / 25 MB / 14 MB — comparable to the macOS-native lane.

Test plan

• Local docker validation: 3 Mach-O arm64 artifacts produced and verified by file(1)
• Trigger GHA release; verify the aarch64-apple-darwin matrix entry succeeds on ubuntu-latest
• Verify uploaded artifacts in the resulting GitHub Release are unchanged in shape (same binaries, same _native.abi3.so layout)

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added support for building macOS ARM64 release artifacts from Linux, improving build flexibility and speed.
  • Enabled cross-platform packaging for the app’s command-line tools and Python extension on the same release lane.
  • Added a containerized workflow for reproducing the macOS ARM64 build process locally.

• Documentation

  • Added setup and usage instructions for the new cross-build container, including verification steps for generated binaries.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 2dfee06d-ec33-4cc8-bd53-054b3295313d

📥 Commits

Reviewing files that changed from the base of the PR and between 15551a6 and b2e6368.

📒 Files selected for processing (5)

• .github/workflows/release-auto.yml
• .github/workflows/template_native_build.yml
• ci/docker-mac-arm64-cross/Dockerfile
• ci/docker-mac-arm64-cross/README.md
• ci/docker-mac-arm64-cross/build.sh

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📝 Walkthrough

Walkthrough

The aarch64-apple-darwin release lane is moved from a macOS runner to ubuntu-latest using soldr + cargo-zigbuild for cross-compilation. A new mac_cross_linux boolean flag threads through the release matrix and the native build template to gate Apple SDK preparation, zigbuild invocations, artifact staging, and strip skipping. A local Docker simulator (ci/docker-mac-arm64-cross/) with build.sh and README is added to reproduce this lane without GitHub Actions.

Changes

aarch64-apple-darwin Linux Cross-Compile Lane

Layer / File(s)	Summary
Release matrix: switch aarch64 to ubuntu + mac_cross_linux flag .github/workflows/release-auto.yml	aarch64-apple-darwin matrix entry changed from macos-latest to ubuntu-latest with mac_cross_linux: true; the flag is passed into the template workflow call.
template_native_build: mac_cross_linux input and build/stage/strip branches .github/workflows/template_native_build.yml	Declares mac_cross_linux boolean input; adds soldr prepare step for Apple SDK; routes fbuild-cli, fbuild-daemon, and fbuild-python through soldr cargo zigbuild; copies lib_native.dylib into staging/_native.abi3.so; skips binary stripping for Mach-O.
Docker image for local cross simulation ci/docker-mac-arm64-cross/Dockerfile, ci/docker-mac-arm64-cross/README.md	New ubuntu:24.04-based Dockerfile that installs uv, pinned soldr binaries, cargo-zigbuild, and zig, setting required env defaults. README explains purpose, build/run commands, and the Mach-O validation check.
build.sh: cross-compile, stage, and validate ci/docker-mac-arm64-cross/build.sh	Script bootstraps Rust via soldr, pre-fetches Apple SDK, builds all three crates with soldr cargo zigbuild, stages artifacts (renaming dylib to _native.abi3.so), and validates each is a Mach-O ARM64 binary via file(1).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• FastLED/fbuild#760: Modifies the same release-auto.yml and template_native_build.yml for cross-compiling the aarch64-apple-darwin lane from Linux with cargo zigbuild, including the same lib_native.dylib → staging/_native.abi3.so staging pattern.
• FastLED/fbuild#153: Introduces soldr integration into template_native_build.yml build workflows, directly underpinning the soldr prepare and soldr cargo zigbuild calls added in this PR.
• FastLED/fbuild#16: Overlaps on the cross-compilation staging of _native.abi3.so and Mach-O-specific strip logic in template_native_build.yml for other cross targets.

Poem

🐇 Hop hop, no Mac in sight,
Ubuntu builds the ARM just right,
zigbuild soars, the Apple SDK found,
Mach-O binaries, arm64-bound!
"NO CHEATING," the file check cries—
A rabbit's cross-compile, Linux-skies! ✨

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/linux-cross-mac-arm64

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