Use dwarf writer to decide whether the module has debug info or not.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62184 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/DwarfWriter.h

@@ -93,6 +93,9 @@ public:
   /// getRecordSourceLineCount - Count source lines.
   unsigned getRecordSourceLineCount();
 
+  /// hasDebugInfo - Return true if debug info intrinsics are seen in 
+  /// this module.
+  bool hasDebugInfo();
 };