chore: import upstream snapshot with attribution

kernel/build.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+# Copyright © 2025-2026 Apple Inc. and the Containerization project authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -e
+
+TARGET_ARCH="${TARGET_ARCH:-$(uname -m)}"
+
+case "${TARGET_ARCH}" in
+  aarch64|arm64)
+    CONFIG=config-arm64
+    KARCH=arm64
+    CROSS_COMPILE=aarch64-linux-gnu-
+    IMAGE_PATH=arch/arm64/boot/Image
+    OUTPUT_NAME=vmlinux-arm64
+    ;;
+  x86_64|amd64)
+    CONFIG=config-x86_64
+    KARCH=x86_64
+    CROSS_COMPILE=x86_64-linux-gnu-
+    IMAGE_PATH=arch/x86/boot/bzImage
+    OUTPUT_NAME=vmlinuz-x86_64
+    ;;
+  *)
+    echo "Unsupported target architecture: ${TARGET_ARCH}" >&2
+    exit 1
+    ;;
+esac
+
+mkdir -p /kbuild
+tar -xf /kernel/source.tar.xz -C /kbuild --strip-components=1
+cp "/kernel/${CONFIG}" /kbuild/.config
+
+(
+  cd /kbuild
+  make ARCH="${KARCH}" CROSS_COMPILE="${CROSS_COMPILE}" olddefconfig && \
+    make ARCH="${KARCH}" CROSS_COMPILE="${CROSS_COMPILE}" -j$((`nproc`-1)) LOCALVERSION="${LOCALVERSION}" && \
+    cp "${IMAGE_PATH}" "/kernel/${OUTPUT_NAME}"
+)