Fix/268 macos cross toolchain

[Galfurian]

Summary

Investigate the remaining macOS cross-compilation failure reported in #268 and use GitHub Actions macOS runners to reproduce it.

Problem / motivation

The macOS cross-toolchain still fails during CMake compiler detection on Apple Silicon.

The reported compile command passes macOS-specific host flags such as -arch arm64 to i686-elf-gcc, which does not recognize them. The same command also contains Homebrew-derived include paths, suggesting that host environment or CMake configuration may still be leaking into the bare-metal cross-compilation setup.

This draft PR is being used to reproduce and isolate the failure on the repository's macOS CI runners before applying a final fix.

Changes

• No functional fix yet.
• Use this branch to reproduce and diagnose the macOS toolchain configuration failure.

Validation

• git diff --check
• Relevant build completed
• Relevant automated tests completed
• Manual validation performed where appropriate

Validation details:

No code changes have been made yet.

The PR is being opened as a draft so the macOS GitHub Actions workflow can
reproduce the failure on a macOS runner.

Scope

• The change is focused on one primary problem.
• Unrelated refactors or cleanup have been left for separate work.
• New behavior is covered by a regression test when practical.
• Documentation was updated when behavior, interfaces, or developer workflow changed.

Related issues

Relates to #268