[Do Not Merge]CHEF-36043: Enable macOS Habitat package build for aarch64-darwin

[sanghinitin]

Summary: Updated habitat/aarch64-darwin/plan.sh to enable native Habitat package builds for macOS (aarch64-darwin) systems. The previous plan was copied from Chef Client and referenced non-existent scripts and build dependencies. This update aligns the Darwin plan with the proven cookstyle root Habitat plan while fixing critical build issues.

Jira: CHEF-34639

Changes:

• Cookstyle-specific build flow: Replaced Chef Client-specific steps (chef-official-distribution, multiple gem binstubs, omnibus/chef-bin packages) with cookstyle-only packaging logic
• Fixed directory context: Added proper cd to HAB_CACHE_SRC_PATH/$pkg_dirname in do_unpack(), do_build(), and do_install() phases to work within Habitat cache instead of accessing host filesystem
• Native extension support: Added core/clang compiler and autotools (core/autoconf, core/automake, core/libtool, core/pkg-config) build dependencies, with CC/CXX environment exports for gem compilation (e.g., prism native extension)
• RubyGems isolation: Hardened do_install() phase by setting HOME and GEM_SPEC_CACHE to writable Habitat locations, and using gem install --local --ignore-dependencies to prevent access to host filesystem paths
• Bundle configuration: Configured Bundler to exclude non-essential gem groups and build cookstyle.gemspec during build phase
• Cleanup: Preserved cleanup logic to remove .github directories and stray Gemfile.lock files from vendored gems

Testing Performed:

• Validated shell syntax with bash -n on updated plan.sh
• Successfully resolved bundler gemspec loading errors by clearing cache and reinstalling dependencies
• Verified native gem compilation support (prism gem) works with clang toolchain
• Tested RubyGems isolation to prevent host filesystem access errors during Habitat build
• Build phases now proceed past dependency installation and reach gem binstub generation

Files Modified:

• habitat/aarch64-darwin/plan.sh (updated from Chef Client template to cookstyle-native macOS build plan)

Evidence:

• Plan syntax validated: bash -n habitat/aarch64-darwin/plan.sh ✓
• Build progresses successfully through dependency resolution, gem building, and binstub generation phases
• Native extensions (prism 1.9.0) compile with clang without errors
• Habitat cache directory isolation prevents /Users filesystem access errors