Use -Werror in hardware/intel/bootstub

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I222823b9b258b0a1edc96c86eb54d941cb80487a
diff --git a/bootstub.mk b/bootstub.mk
index 97df35d..fca23e6 100644
--- a/bootstub.mk
+++ b/bootstub.mk
@@ -14,6 +14,7 @@
 LOCAL_SRC_FILES_x86 := $(BOOTSTUB_SRC_FILES_x86)
 ANDROID_TOOLCHAIN_FLAGS := -m32 -ffreestanding
 LOCAL_CFLAGS := $(ANDROID_TOOLCHAIN_FLAGS) -Wall -O1 -DCMDLINE_SIZE=${CMDLINE_SIZE} -DAOSP_HEADER_ADDRESS=$(BOOTSTUB_AOSP_HEADER_ADDRESS) $(BOOTSTUB_CFLAGS)
+LOCAL_CFLAGS += -Werror
 LOCAL_ASFLAGS := -DSTACK_OFFSET=$(BOOTSTUB_STACK_OFFSET)
 LOCAL_C_INCLUDES = system/core/mkbootimg
 LOCAL_MODULE := $(BOOTSTUB_BINARY).bin