thread_pthread.c: fix non-sleepy timer thread build

I guess everybody has poll() and fcntl() nowadays, as
the non-sleepy timer thread build has been broken for
years, now.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63682 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

thread_pthread.c

@@ -1608,9 +1608,10 @@ rb_thread_create_timer_thread(void)
 #endif
 	    return;
 	}
-
+#if USE_SLEEPY_TIMER_THREAD
 	/* validate pipe on this process */
 	timer_thread_pipe.owner_process = getpid();
+#endif
 	timer_thread.created = 1;
     }
 }