u-boot: create signed bootscript at build time

before this was as binary in git which make no real sense.

Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>
Acked-by: Peter Müller <peter.mueller@ipfire.org>
Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>

lfs/u-boot

@@ -240,6 +240,9 @@ endif
 
 	# config (uEnv.txt and boot.*)
 	cp -vf $(DIR_SRC)/config/u-boot/* /boot/
+	# create signed binary boot script (boot.scr)
+	mkimage -C none -A arm -T script -d /boot/boot.cmd /boot/boot.scr
+
 	# patch real Kernel version to uEnv.txt
 	sed -e "s/xxxKVERxxx/$(KVER)/g" -i /boot/uEnv.txt