Subzero: Emit ARM build-attributes in the file scope (as header).

src/IceGlobalContext.h

Index: src/IceGlobalContext.h
diff --git a/src/IceGlobalContext.h b/src/IceGlobalContext.h
index 9fb997c9d1547dffff31c29d06c7f814fe22cf54..763a75b487ced3554f3bf53127106f792eabdf31 100644
--- a/src/IceGlobalContext.h
+++ b/src/IceGlobalContext.h
@@ -300,6 +300,9 @@ public:
   // Notifies that no more work will be added to the work queue.
   void optQueueNotifyEnd() { OptQ.notifyEnd(); }
 
+  // Emit file header for output file.
+  void emitFileHeader();
+
   void emitQueueBlockingPush(EmitterWorkItem *Item);
   EmitterWorkItem *emitQueueBlockingPop();
   void emitQueueNotifyEnd() { EmitQ.notifyEnd(); }