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/native/dalvik_system_ZygoteHooks.cc b/runtime/native/dalvik_system_ZygoteHooks.cc
index 65002df..887eee0 100644
--- a/runtime/native/dalvik_system_ZygoteHooks.cc
+++ b/runtime/native/dalvik_system_ZygoteHooks.cc
@@ -121,6 +121,7 @@
   if ((debug_flags & DEBUG_NATIVE_DEBUGGABLE) != 0) {
     runtime->AddCompilerOption("--debuggable");
     runtime->AddCompilerOption("--generate-debug-info");
+    runtime->SetNativeDebuggable(true);
     debug_flags &= ~DEBUG_NATIVE_DEBUGGABLE;
   }