u-boot-iot2050: Add an explicit env to mark secure boot building

The existence of keys folder implying the secure boot building only
applies to scenarios that private key is locally accessible.

In cases when a clear private key is not available, an explicit
environment to mark the secure boot building is required.

Signed-off-by: Baocheng Su <baocheng.su@siemens.com>

recipes-bsp/u-boot/files/rules.tmpl

@@ -10,7 +10,7 @@ SET_CROSS_BUILD_TOOLS=CROSS_BUILD_TOOLS=y
 endif
 
 override_dh_auto_build:
-	if [ -e keys ]; then \
+	if [ "${SB_SIGN}" = "1" ]; then \
 		tools/key2dtsi.py -c -s keys/custMpk.pem arch/arm/dts/custMpk.dtsi; \
 	fi
 	$(MAKE) $(PARALLEL_MAKE) ${U_BOOT_CONFIG}
@@ -22,7 +22,7 @@ override_dh_auto_build:
 	else \
 		./scripts/get_default_envs.sh >u-boot-initial-env; \
 	fi
-	if [ -e keys ]; then \
+	if [ "${SB_SIGN}" = "1" ]; then \
 		tools/iot2050-sign-fw.sh keys/custMpk.pem ${FIRMWARE_SECURE_VER}; \
 	fi
 	$(MAKE) $(PARALLEL_MAKE) $(SET_CROSS_BUILD_TOOLS) NO_SDL=1 tools-only envtools

recipes-bsp/u-boot/u-boot-iot2050.inc

@@ -41,8 +41,11 @@ DEBIAN_BUILD_DEPENDS:append:secureboot = ", python3-pycryptodome:native, \
 DEPENDS:append:otpcmd = " secure-boot-otp-provisioning"
 DEBIAN_BUILD_DEPENDS:append:otpcmd = ", secure-boot-otp-provisioning"
 
+SB_SIGN = "0"
+SB_SIGN:secureboot = "1"
+
 TEMPLATE_FILES += "rules.tmpl"
-TEMPLATE_VARS += "FIRMWARE_SECURE_VER"
+TEMPLATE_VARS += "FIRMWARE_SECURE_VER SB_SIGN"
 
 U_BOOT_CONFIG_PACKAGE = "1"