Allow modules to override the default NOTICE file.

It's useful in projects where different top level modules have
different licenses associated with them.

Change-Id: I6214fdeaf038d7a054473f1fbab5315db9b824e4
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 91dfdac..656f327 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -192,6 +192,7 @@
 LOCAL_INIT_RC:=
 LOCAL_MODULE_HOST_OS:=
 LOCAL_FINDBUGS_FLAGS:=
+LOCAL_NOTICE_FILE:=
 
 # arch specific variables
 LOCAL_SRC_FILES_$(TARGET_ARCH):=