fix(macos): build Node 26 on macos-15 and disable LTO

[robertsLando]

Problem

The macOS Node 26 builds fail in build-all.yml:

• macos-arm64 (26) fails fast in the compile step:

  ../deps/v8/src/base/atomicops.h:90: error: no member named 'atomic_ref' in namespace 'std'
  

  std::atomic_ref is a C++20 library feature that V8 in Node 26 now uses in atomicops.h. The job was pinned to runs-on: macos-14, whose newest available Xcode is 16.2 — its libc++ predates std::atomic_ref. Xcode 16.3+ (requires macOS 15) ships the libc++ that has it. Confirmed empirically: the macos-15-intel x64 job compiles straight past atomicops.h.

• macos-x64 (24) and (26) hit GitHub Actions' 6h job limit. getConfigureArgs force-enabled --enable-lto for every non-Windows build, and the LTO link phase is enormously slow on the Intel runner.

Both are the macOS issues described in #170.

Changes

• build-macos.yml — bump the arm64 runner macos-14 → macos-15 (Xcode 16.4 → libc++ with std::atomic_ref).
• lib/build.ts — skip --enable-lto for macOS in getConfigureArgs (Windows was already excluded).
• build-macos.yml — add ccache (actions/cache + PKG_BUILD_PATH under CCACHE_BASEDIR) and GNU make v4 to both macOS jobs, so rebuilds stay fast and make -j works correctly.

Notes

• PKG_BUILD_PATH is already supported upstream (build.ts:18); pointing it under the workspace keeps ccache paths stable across runs.
• The first run after this lands has no warm cache, so it relies on the LTO removal alone to fit within 6h; subsequent runs benefit from ccache.
• Action versions (checkout@v6, setup-node@v6, upload-artifact@v7) and the [22, 24, 26] matrix are unchanged.

Refs #170

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This pull request fixes macOS build failures/timeouts when building newer Node.js versions (notably Node 26) in CI by updating the macOS runner image/toolchain and reducing macOS build time.

Changes:

• Disable --enable-lto for macOS builds to avoid excessively long link phases on GitHub Actions runners.
• Move macOS arm64 CI to macos-15 to pick up a newer Xcode/libc++ that supports std::atomic_ref (needed by V8 in Node 26).
• Add ccache + GNU Make v4 to macOS CI jobs and cache the compiler cache to speed up rebuilds.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
lib/build.ts	Skips enabling LTO when the target platform is macOS to reduce CI build time.
.github/workflows/build-macos.yml	Updates macOS runner selection and adds ccache/GNU Make setup + caching for faster, more reliable CI builds.

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