Exclude subdirectories when pruning the dex cache.

This requires a companion package manager change to prune
each instruction specific dex cache individually.

bug: 15677279

Change-Id: I5891981512bde20e49bff65b1842c28886f2b177
diff --git a/cmds/installd/installd.h b/cmds/installd/installd.h
index c1e6e0f..f193b46 100644
--- a/cmds/installd/installd.h
+++ b/cmds/installd/installd.h
@@ -220,4 +220,4 @@
 int linklib(const char* target, const char* source, int userId);
 int idmap(const char *target_path, const char *overlay_path, uid_t uid);
 int restorecon_data();
-int prune_dex_cache();
+int prune_dex_cache(const char* subdir);