[openwrt/openwrt] build: add Mikrotik NOR RouterBOOT v7 image build

[LEDE Commits]

dangole pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/f473d15816c78a1580ed036107428ed7d51b3142

commit f473d15816c78a1580ed036107428ed7d51b3142
Author: John Thomson <git at johnthomson.fastmail.com.au>
AuthorDate: Sun Jan 22 21:34:43 2023 +1000

    build: add Mikrotik NOR RouterBOOT v7 image build
    
    Add build step 'kernel-pack-npk' which uses 'npk_pack_kernel' which is now
    part of firmware-utils to enable wrapping the kernel inside a MikroTik NPK
    package.
    
    Signed-off-by: John Thomson <git at johnthomson.fastmail.com.au>
    Signed-off-by: Daniel Golle <daniel at makrotopia.org>
---
 include/image-commands.mk | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/image-commands.mk b/include/image-commands.mk
index 781f6ad03b..ad57dfd49b 100644
--- a/include/image-commands.mk
+++ b/include/image-commands.mk
@@ -557,6 +557,11 @@ define Build/gl-qsdk-factory
 		$(KDIR_TMP)/$(notdir $(BOOT_SCRIPT))
 endef
 
+define Build/kernel-pack-npk
+	$(STAGING_DIR_HOST)/bin/npk_pack_kernel $@ $@.npk
+	mv $@.npk $@
+endef
+
 define Build/linksys-image
 	let \
 		size="$$(stat -c%s $@)" \