Learn that __DATA,__objc_classrefs is not atomized via symbols.

This should hopefully fix objc on AArch64.

llvm-svn: 228976
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
index 6c554fd..0d9385d 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
@@ -134,6 +134,10 @@
       RefSec.getSectionName() == "__cfstring")
     return false;
 
+  if (RefSec.getSegmentName() == "__DATA" &&
+      RefSec.getSectionName() == "__objc_classrefs")
+    return false;
+
   return true;
 }