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
(cherry picked from commit 7aa88748f6ec4e53333d1a15747bc44826ccc410)
diff --git a/uncrypt/Android.mk b/uncrypt/Android.mk
index bb276ed..97fc708 100644
--- a/uncrypt/Android.mk
+++ b/uncrypt/Android.mk
@@ -17,16 +17,15 @@
 include $(CLEAR_VARS)
 
 LOCAL_CLANG := true
-
 LOCAL_SRC_FILES := uncrypt.cpp
-
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/..
-
 LOCAL_MODULE := uncrypt
-
-LOCAL_STATIC_LIBRARIES := libbootloader_message libbase \
-                          liblog libfs_mgr libcutils \
-
+LOCAL_STATIC_LIBRARIES := libbootloader_message \
+                          libbase \
+                          liblog \
+                          libfs_mgr \
+                          libcutils
+LOCAL_CFLAGS := -Werror
 LOCAL_INIT_RC := uncrypt.rc
 
 include $(BUILD_EXECUTABLE)