Provide the option to enable debug information during tar backups

Change-Id: Ibdb060d334c8f799a283f1bcef4a369d5555c975
diff --git a/libtar/Android.mk b/libtar/Android.mk
index 9a35c7b..9b051e6 100755
--- a/libtar/Android.mk
+++ b/libtar/Android.mk
@@ -25,6 +25,10 @@
     endif
 endif
 
+ifeq ($(TW_LIBTAR_DEBUG),true)
+    LOCAL_CFLAGS += -DTW_LIBTAR_DEBUG
+endif
+
 include $(BUILD_SHARED_LIBRARY)
 
 # Build static library
@@ -52,4 +56,8 @@
     endif
 endif
 
+ifeq ($(TW_LIBTAR_DEBUG),true)
+    LOCAL_CFLAGS += -DTW_LIBTAR_DEBUG
+endif
+
 include $(BUILD_STATIC_LIBRARY)