build: guard INITRAMFS_ARCHIVE in stage_kernel_build for incremental runs

initramfs: ensure essential dirs incl. /home exist during finalize and validate 'home' as essential item

scripts/build.sh

@@ -397,6 +397,17 @@ function main_build_process() {
     
     function stage_kernel_build() {
         local kernel_output="${DIST_DIR}/vmlinuz.efi"
+
+        # Ensure INITRAMFS_ARCHIVE is set even if initramfs_create/test were skipped previously
+        if [[ -z "${INITRAMFS_ARCHIVE:-}" ]]; then
+            local archive_path="${DIST_DIR}/initramfs.cpio.xz"
+            if [[ "${archive_path}" != /* ]]; then
+                archive_path="${PROJECT_ROOT}/${archive_path#./}"
+            fi
+            export INITRAMFS_ARCHIVE="${archive_path}"
+            log_debug "stage_kernel_build: defaulting INITRAMFS_ARCHIVE=${INITRAMFS_ARCHIVE}"
+        fi
+
         kernel_build_with_initramfs "$KERNEL_CONFIG" "$INITRAMFS_ARCHIVE" "$kernel_output"
         export KERNEL_OUTPUT="$kernel_output"
     }