Support more precise package exclusion from JAR files.

Allow LOCAL_JAR_PACKAGES to work on subpackages.  Previously it
only worked on top-level packages due to a bug in how the directories
were recursively deleted.

Add LOCAL_JAR_EXCLUDE_PACKAGES to allow specific subpackages to
be excluded.  This rule applies after LOCAL_JAR_PACKAGES has
selected which packages to include.  It may also be used independently.

Change-Id: Ibd0e495be1a20c84b59c9da132e92100ef3f8705
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index f30e170..7d1cd60 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -137,6 +137,7 @@
 LOCAL_ADDRESS_SANITIZER:=
 LOCAL_JAR_EXCLUDE_FILES:=
 LOCAL_JAR_PACKAGES:=
+LOCAL_JAR_EXCLUDE_PACKAGES:=
 LOCAL_LINT_FLAGS:=
 LOCAL_SOURCE_FILES_ALL_GENERATED:= # '',true
 # Don't delete the META_INF dir when merging static Java libraries.