u-boot.mk: pass CROSS_COMPILE during config

Avoids running into unset architecture specific config symbols

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/u-boot.mk

@@ -110,10 +110,10 @@ define Build/U-Boot/Target
 endef
 
 define Build/Configure/U-Boot
-	+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR) $(UBOOT_CONFIGURE_VARS) $(UBOOT_CONFIG)_config
+	+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR) CROSS_COMPILE=$(TARGET_CROSS) $(UBOOT_CONFIGURE_VARS) $(UBOOT_CONFIG)_config
 	$(if $(strip $(UBOOT_CUSTOMIZE_CONFIG)),
 		$(PKG_BUILD_DIR)/scripts/config --file $(PKG_BUILD_DIR)/.config $(UBOOT_CUSTOMIZE_CONFIG)
-		+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR) $(UBOOT_CONFIGURE_VARS) oldconfig)
+		+$(MAKE) $(PKG_JOBS) -C $(PKG_BUILD_DIR) CROSS_COMPILE=$(TARGET_CROSS) $(UBOOT_CONFIGURE_VARS) oldconfig)
 endef
 
 ifndef UBOOT_USE_INTREE_DTC