[ELF] - Fixing buildbot.

http://lab.llvm.org:8011/builders/lld-x86_64-darwin13/builds/11517/steps/build_Lld/logs/stdio

llvm-svn: 310705
diff --git a/lld/ELF/MapFile.cpp b/lld/ELF/MapFile.cpp
index 1d8a44f..f2739e2 100644
--- a/lld/ELF/MapFile.cpp
+++ b/lld/ELF/MapFile.cpp
@@ -58,7 +58,7 @@
           V.push_back(DR);
       } else if (auto *DC = dyn_cast<DefinedCommon>(B)) {
         if (InX::Common)
-          V.push_back(cast<DefinedCommon>(B));
+          V.push_back(DC);
       }
     }
   }