ART: Use kNormThreadPriority for UnstartedRuntime

Normalize the compiler thread's perceived priority to make the
result independent of the compilation environment.

Bug: 128865240
Test: m
Change-Id: I5f8bc144d05453c5df603fef221ce22d66eff546
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 526413b..9080418 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -1156,7 +1156,7 @@
     CHECK(Thread::Current()->IsExceptionPending());
     return nullptr;
   }
-  jint thread_priority = GetNativePriority();
+  jint thread_priority = kNormThreadPriority;  // Always normalize to NORM priority.
   jboolean thread_is_daemon = as_daemon;
 
   ScopedLocalRef<jobject> peer(env, env->AllocObject(WellKnownClasses::java_lang_Thread));