mips has no sa_restorer.

This change should be a no-op, because we're not using
it anyway. FaultManager doesn't seem designed for inheritance,
so I can't put this in an arch specific subclass.

Change-Id: I2eaabdf2a77ef558c59139344f8654cf3ccafa86
diff --git a/runtime/fault_handler.cc b/runtime/fault_handler.cc
index 6399c0d..f9f3e25 100644
--- a/runtime/fault_handler.cc
+++ b/runtime/fault_handler.cc
@@ -53,7 +53,9 @@
   action.sa_sigaction = art_fault_handler;
   sigemptyset(&action.sa_mask);
   action.sa_flags = SA_SIGINFO | SA_ONSTACK;
+#if !defined(__mips__)
   action.sa_restorer = nullptr;
+#endif
   sigaction(SIGSEGV, &action, &oldaction_);
 }