Add LOCAL_DONT_DELETE_JAR_META_INF

To support to not delete META_INF directory from the static Java
libraries.

Change-Id: I720bfa059c43dd457a74a0c60bb6797aa408ecaf
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index a389915..343345f 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -125,6 +125,8 @@
 LOCAL_JAR_EXCLUDE_FILES:=
 LOCAL_LINT_FLAGS:=
 LOCAL_SOURCE_FILES_ALL_GENERATED:= # '',true
+# Don't delete the META_INF dir when merging static Java libraries.
+LOCAL_DONT_DELETE_JAR_META_INF:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.