uncrypt: split libbootloader_message_writer for reuse.

init and vold also need to write bootloader message, so
split this function from uncrypt into a separate library.

Bug: 27176738
Change-Id: If9b0887b4f6ffab6162d9cb47a6ceb7eedd60b4d
diff --git a/uncrypt/Android.mk b/uncrypt/Android.mk
index 6422cb2..09cfdfc 100644
--- a/uncrypt/Android.mk
+++ b/uncrypt/Android.mk
@@ -15,6 +15,15 @@
 LOCAL_PATH := $(call my-dir)
 
 include $(CLEAR_VARS)
+LOCAL_CLANG := true
+LOCAL_SRC_FILES := bootloader_message_writer.cpp
+LOCAL_MODULE := libbootloader_message_writer
+LOCAL_STATIC_LIBRARIES := libbase libfs_mgr
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/..
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
+include $(BUILD_STATIC_LIBRARY)
+
+include $(CLEAR_VARS)
 
 LOCAL_CLANG := true
 
@@ -24,7 +33,8 @@
 
 LOCAL_MODULE := uncrypt
 
-LOCAL_STATIC_LIBRARIES := libbase liblog libfs_mgr libcutils
+LOCAL_STATIC_LIBRARIES := libbootloader_message_writer libbase \
+                          liblog libfs_mgr libcutils \
 
 LOCAL_INIT_RC := uncrypt.rc