Fix O0 build.

Use builtin for x86 cmpxchg as inline asm defeats O0 register allocator.
Add missing const static field definitions.

Change-Id: I10e41ddea90ce156cdb1ca43f4bf9d6d4b6c4259
diff --git a/src/dex2oat.cc b/src/dex2oat.cc
index 65b3ddb..235c068 100644
--- a/src/dex2oat.cc
+++ b/src/dex2oat.cc
@@ -640,6 +640,8 @@
   pthread_attr_t attr_;
   pthread_t pthread_;
 };
+const unsigned int WatchDog::kWatchDogWarningSeconds;
+const unsigned int WatchDog::kWatchDogTimeoutSeconds;
 
 static int dex2oat(int argc, char** argv) {
   InitLogging(argv);