Turn on -Werror for recovery

Also remove the 0xff comparison when validating the bootloader
message fields. As the fields won't be erased to 0xff after we
remove the MTD support.

Bug: 28202046
Test: The recovery folder compiles for aosp_x86-eng
Change-Id: Ibb30ea1b2b28676fb08c7e92a1e5f7b6ef3247ab
diff --git a/Android.mk b/Android.mk
index 76e99b6..7fa98b0 100644
--- a/Android.mk
+++ b/Android.mk
@@ -66,7 +66,7 @@
 RECOVERY_API_VERSION := 3
 RECOVERY_FSTAB_VERSION := 2
 LOCAL_CFLAGS += -DRECOVERY_API_VERSION=$(RECOVERY_API_VERSION)
-LOCAL_CFLAGS += -Wno-unused-parameter
+LOCAL_CFLAGS += -Wno-unused-parameter -Werror
 LOCAL_CLANG := true
 
 LOCAL_C_INCLUDES += \
@@ -146,6 +146,7 @@
     verifier.cpp \
     ui.cpp
 LOCAL_STATIC_LIBRARIES := libcrypto_utils libcrypto libbase
+LOCAL_CFLAGS := -Werror
 include $(BUILD_STATIC_LIBRARY)
 
 include $(LOCAL_PATH)/minui/Android.mk \