feat(steps-guix): build linux64 kernel and switch via jump with backup

steps-guix/linux-6.12.74/pass1.sh

@@ -0,0 +1,38 @@
+# SPDX-FileCopyrightText: 2026 Luo Yanpan
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+: "${KERNEL_SYSROOT:=/kernel-toolchain}"
+: "${KERNEL_TARGET:=x86_64-unknown-linux-musl}"
+
+kernel_env() {
+    export PATH="${KERNEL_SYSROOT}/bin:${PATH}"
+    export HOSTCFLAGS="-I${KERNEL_SYSROOT}/include"
+    export HOSTLDFLAGS="-L${KERNEL_SYSROOT}/lib"
+    export LD_LIBRARY_PATH="${KERNEL_SYSROOT}/lib:${LD_LIBRARY_PATH}"
+}
+
+kernel_make() {
+    kernel_env
+    make "${MAKEJOBS}" \
+        ARCH=x86_64 \
+        CROSS_COMPILE="${KERNEL_SYSROOT}/bin/${KERNEL_TARGET}-" \
+        "$@"
+}
+
+src_prepare() {
+    default
+}
+
+src_configure() {
+    kernel_make defconfig
+}
+
+src_compile() {
+    kernel_make
+}
+
+src_install() {
+    install -D -m 644 arch/x86/boot/bzImage \
+        "${DESTDIR}/boot/vmlinuz-linux64"
+}

steps-guix/linux-6.12.74/sources

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+f https://linux-libre.fsfla.org/pub/linux-libre/releases/6.12.74-gnu/linux-libre-6.12.74-gnu.tar.xz d0071b065a7a5ba5ea9f638828beb113774f9f043182cbf2c6b205d403f074f5