Do not JIT boot image during native-debugging (keep AOT code instead).

The performance impact is currently significant and being able
to debug framework is not our primary goal for native debugging.

Change-Id: I3366c2a6317004f9dd16700b271a6c9b974f1c6e
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index c8085fb..78e00fd 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -203,6 +203,7 @@
       implicit_suspend_checks_(false),
       no_sig_chain_(false),
       is_native_bridge_loaded_(false),
+      is_native_debuggable_(false),
       zygote_max_failed_boots_(0),
       experimental_flags_(ExperimentalFlags::kNone),
       oat_file_manager_(nullptr),