Use latest LLVM and cache libc++ build. #180

	name: Clang

	on:
	push:
	branches:
	- '**'
	pull_request:
	branches:
	- main
	schedule:
	- cron: '0 0 * * 0'

	jobs:
	build:
	runs-on: ${{ matrix.os }}

	strategy:
	matrix:
	os: [ubuntu-latest, macos-latest]
	std_version: [20, 23]

	steps:
	- name: Checkout
	uses: actions/checkout@v4

	- name: Add homebrew to PATH (Linux only)
	if: runner.os == 'Linux'
	run: \|
	echo "/home/linuxbrew/.linuxbrew/bin" >> $GITHUB_PATH

	- name: Get LLVM and Ninja via Homebrew
	run: \|
	brew install llvm ninja
	echo "CC=$(brew --prefix llvm)/bin/clang" >> "$GITHUB_ENV"
	echo "CXX=$(brew --prefix llvm)/bin/clang++" >> "$GITHUB_ENV"

	- name: Cache libc++ build
	id: cache-libcxx
	uses: actions/cache@v4
	with:
	path: llvm-project/build
	key: ${{ runner.os }}-libcxx

	- name: Make local build of libc++ with Standard Library Module (when cache miss)
	if: steps.cache-libcxx.outputs.cache-hit != 'true'
	run: \|
	git clone https://github.com/llvm/llvm-project.git
	cd llvm-project
	mkdir build
	cmake -G Ninja -S runtimes -B build \
	-DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi;libunwind" \
	-DLLVM_INCLUDE_TESTS=OFF
	ninja -C build

	- name: Configure
	run: \|
	mkdir build
	cmake -S . -G Ninja -B build \
	-DCMAKE_CXX_STANDARD=${{ matrix.std_version }} \
	-DLIBCXX_BUILD=${{ github.workspace }}/llvm-project/build

	- name: Build
	run: \|
	cmake --build build -t CppStandardLibraryModule --config Release

	- name: Run executable
	run: \|
	./build/CppStandardLibraryModule

Provide feedback