core: semantic change, KERNELSOURCE must be explicitly 'none' to avoid kernel compilation (not unset)

config/sources/families/include/uefi_common.inc

@@ -15,7 +15,7 @@ declare -g DISTRO_GENERIC_KERNEL=no
 case "${BRANCH}" in
 
 	ddk)
-		# This will force `unset KERNELSOURCE` later; no kernel will be built.
+		# This will force `KERNELSOURCE='none'` later; no kernel will be built.
 		# Instead, the distro's default linux-generic kernel will be installed.
 		# rpardini: For some regrettable reason, most of this logic is in the grub extension.
 		declare -g DISTRO_GENERIC_KERNEL=yes

extensions/grub.sh

@@ -63,7 +63,7 @@ function extension_prepare_config__prepare_grub_standard() {
 
 	if [[ "${DISTRO_GENERIC_KERNEL}" == "yes" ]]; then
 		declare -g IMAGE_INSTALLED_KERNEL_VERSION="${DISTRO_KERNEL_VER}"
-		unset KERNELSOURCE                     # This should make Armbian skip most stuff. At least, I hacked it to.
+		declare -g KERNELSOURCE='none'         # We need to be explicit we don't want a kernel built.
 		declare -g INSTALL_ARMBIAN_FIRMWARE=no # Should skip build and install of Armbian-firmware.
 	else
 		declare -g KERNELDIR="linux-uefi-${LINUXFAMILY}" # Avoid sharing a source tree with others, until we know it's safe.

lib/functions/compilation/kernel-git.sh

@@ -8,7 +8,7 @@
 # https://github.com/armbian/build/
 
 function kernel_prepare_git() {
-	[[ -z $KERNELSOURCE ]] && return 0 # do nothing if no kernel source... but again, why were we called then?
+	[[ "${KERNELSOURCE}" == 'none' ]] && return 0 # do nothing if no kernel source... but again, why were we called then?
 
 	# validate kernel_git_bare_tree is set
 	if [[ -z "${kernel_git_bare_tree}" ]]; then

lib/functions/image/rootfs-to-image.sh

@@ -86,7 +86,7 @@ function create_image_from_sdcard_rootfs() {
 	PRE_UPDATE_INITRAMFS
 
 	# stage: create final initramfs
-	[[ -n $KERNELSOURCE ]] && {
+	[[ "${KERNELSOURCE}" != 'none' ]] && {
 		update_initramfs "$MOUNT"
 	}
 

lib/functions/main/build-packages.sh

@@ -11,7 +11,7 @@ function determine_artifacts_to_build_for_image() {
 	if [[ "${BOOTCONFIG}" != "none" ]]; then
 		artifacts_to_build+=("uboot")
 	fi
-	if [[ -n $KERNELSOURCE ]]; then
+	if [[ "${KERNELSOURCE}" != 'none' ]]; then
 		artifacts_to_build+=("kernel")
 	fi
 

lib/functions/main/config-prepare.sh

@@ -220,7 +220,7 @@ function config_post_main() {
 	# So we gotta explictly know the major.minor to be able to do that scheme.
 	# If we don't know, we could use BRANCH as reference, but that changes over time, and leads to wastage.
 	if [[ "${skip_kernel:-"no"}" != "yes" ]]; then
-		if [[ -n "${KERNELSOURCE}" ]]; then
+		if [[ "${KERNELSOURCE}" != 'none' ]]; then
 			if [[ "x${KERNEL_MAJOR_MINOR}x" == "xx" ]]; then
 				display_alert "Problem: after configuration, there's not enough kernel info" "Might happen if you used the wrong BRANCH. Make sure 'BRANCH=${BRANCH}' is valid." "err"
 				# if we have KERNEL_TARGET set.

lib/functions/rootfs/distro-agnostic.sh

@@ -274,14 +274,14 @@ function install_distribution_agnostic() {
 
 	call_extension_method "pre_install_kernel_debs" <<- 'PRE_INSTALL_KERNEL_DEBS'
 		*called before installing the Armbian-built kernel deb packages*
-		It is not too late to `unset KERNELSOURCE` here and avoid kernel install.
+		It is not too late to `KERNELSOURCE='none'` here and avoid kernel install.
 	PRE_INSTALL_KERNEL_DEBS
 
 	# default IMAGE_INSTALLED_KERNEL_VERSION, will be parsed from Kernel version in the installed deb package.
 	IMAGE_INSTALLED_KERNEL_VERSION="generic"
 
 	# install kernel: image/dtb/headers
-	if [[ -n $KERNELSOURCE ]]; then
+	if [[ "${KERNELSOURCE}" != "none" ]]; then
 		install_artifact_deb_chroot "linux-image"
 
 		if [[ "${KERNEL_BUILD_DTBS:-"yes"}" == "yes" ]]; then