examples: add --viper-output to the hello example

We add --viper-output to the hello example. This will let us test that
future changes do not break the Viper export functionality.

Signed-off-by: Zoltan A. Kocsis <z.kocsis@unsw.edu.au>

Author: zaklogician

example/hello/Makefile

@@ -67,4 +67,4 @@ $(BUILD_DIR)/hello.elf: $(addprefix $(BUILD_DIR)/, $(HELLO_OBJS))
 	$(LD) $(LDFLAGS) $^ $(LIBS) -o $@
 
 $(IMAGE_FILE) $(REPORT_FILE): $(addprefix $(BUILD_DIR)/, $(IMAGES)) hello.system
-	$(MICROKIT_TOOL) hello.system --search-path $(BUILD_DIR) --board $(MICROKIT_BOARD) --config $(MICROKIT_CONFIG) -o $(IMAGE_FILE) -r $(REPORT_FILE)
+	$(MICROKIT_TOOL) hello.system --search-path $(BUILD_DIR) --viper-output ${BUILD_DIR}/viper --board $(MICROKIT_BOARD) --config $(MICROKIT_CONFIG) -o $(IMAGE_FILE) -r $(REPORT_FILE)