Allow custom bootloader msg offset in block misc

Use board define BOARD_RECOVERY_BLDRMSG_OFFSET with a decimal integer
to define a custom offset where the bootloader message should be
read/written.

Change-Id: Id13a23dd41bb7d907b96d657b8e21eb839dfeaa9
diff --git a/Android.mk b/Android.mk
index c864ff0..05111c0 100644
--- a/Android.mk
+++ b/Android.mk
@@ -335,6 +335,10 @@
 LOCAL_SHARED_LIBRARIES += libc liblog libcutils libmtdutils
 LOCAL_STATIC_LIBRARIES += libmincrypttwrp
 
+ifneq ($(BOARD_RECOVERY_BLDRMSG_OFFSET),)
+    LOCAL_CFLAGS += -DBOARD_RECOVERY_BLDRMSG_OFFSET=$(BOARD_RECOVERY_BLDRMSG_OFFSET)
+endif
+
 include $(BUILD_SHARED_LIBRARY)
 
 commands_recovery_local_path := $(LOCAL_PATH)