Let dalvikvm default based on persist.sys.dalvik.vm.lib

Change-Id: I0e2aa9b1227d9665c37366d6d7bdca2b6c009271
diff --git a/dalvikvm/dalvikvm.cc b/dalvikvm/dalvikvm.cc
index dd68da0..1672099 100644
--- a/dalvikvm/dalvikvm.cc
+++ b/dalvikvm/dalvikvm.cc
@@ -124,7 +124,7 @@
   //
   // [Do we need to catch & handle "-jar" here?]
   bool need_extra = false;
-  const char* lib = "libdvm.so";
+  const char* lib = NULL;
   const char* what = NULL;
   int curr_opt, arg_idx;
   for (curr_opt = arg_idx = 0; arg_idx < argc; arg_idx++) {