Do not add linker the _r_debug.r_map on link_image

Bug: http://b/27533895
Change-Id: Idd0fb06a5d9f400c0608ae532cc4c575211810fa
(cherry picked from commit e97d8ed70e44db619de9975a43ed2d1509653d74)
diff --git a/linker/linker.h b/linker/linker.h
index 104d615..f5bab84 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -310,6 +310,7 @@
   }
 
   bool is_linked() const;
+  bool is_linker() const;
   bool is_main_executable() const;
 
   void set_linked();