test

    systemd-nspawn -D "$CHROOT_DIR" --pipe -- bash -c '

        set -e

        apt-get install -y --no-install-recommends linux-libc-dev

        # Copy linux and asm-generic headers

        rm -rf /usr/local/musl/include/linux /usr/local/musl/include/asm-generic /usr/local/musl/include/asm

        cp -a /usr/include/linux /usr/local/musl/include/

        cp -a /usr/include/asm-generic /usr/local/musl/include/

        # Debian stores arch-specific headers under multiarch path

        if [ -d /usr/include/x86_64-linux-gnu/asm ]; then

        # Find arch-specific asm headers using dpkg

        ASM_DIR=$(dpkg -L linux-libc-dev | grep "/asm$" | head -1)

        if [ -n "$ASM_DIR" ] && [ -d "$ASM_DIR" ]; then

            echo "Found asm headers at: $ASM_DIR"

            cp -a "$ASM_DIR" /usr/local/musl/include/

        elif [ -d /usr/include/x86_64-linux-gnu/asm ]; then

            cp -a /usr/include/x86_64-linux-gnu/asm /usr/local/musl/include/

        elif [ -d /usr/include/asm ]; then

            cp -a /usr/include/asm /usr/local/musl/include/

        else

            # Generate minimal asm headers from asm-generic

            echo "WARNING: No asm headers found, generating from asm-generic"

            mkdir -p /usr/local/musl/include/asm

            for f in /usr/local/musl/include/asm-generic/*.h; do

                name=$(basename $f)

                echo "#include <asm-generic/${name}>" > /usr/local/musl/include/asm/${name}

                name=$(basename "$f")

                echo "#include <asm-generic/${name}>" > "/usr/local/musl/include/asm/${name}"

            done

        fi

        echo "==> Kernel headers installed"

        # Verify critical header exists

        if [ ! -f /usr/local/musl/include/asm/types.h ]; then

            echo "ERROR: asm/types.h still missing after install!"

            echo "Contents of linux-libc-dev:"

            dpkg -L linux-libc-dev | grep asm | head -20

            exit 1

        fi

        echo "==> Kernel headers installed (asm/types.h verified)"

    '

}

        # LLVM 18 requires the unified runtimes build

        cd /tmp

        LLVM_TAG=llvmorg-${LLVM_VERSION}.1.8

        if [ ! -d /tmp/llvm-project-\${LLVM_TAG} ]; then

            wget -q https://github.com/llvm/llvm-project/archive/refs/tags/\${LLVM_TAG}.tar.gz -O llvm-project.tar.gz

            tar xf llvm-project.tar.gz

        fi

        LLVM_SRC=/tmp/llvm-project-\${LLVM_TAG}

        # Clean stale build to avoid cached failures

        rm -rf /tmp/build-runtimes

        # Unified runtimes build: libunwind + libc++abi + libc++

        mkdir -p /tmp/build-runtimes && cd /tmp/build-runtimes

        cmake \${LLVM_SRC}/runtimes -G Ninja \