Add pointerKind() method to the MachO ArchHandler's.  NFC.

The ObjCPass is going to need to create pointer sized relocations in
the ObjC sections.  This method will be used to give us a target independent
way of getting the correct kind for the refererence.

llvm-svn: 259441
diff --git a/lld/lib/ReaderWriter/MachO/ArchHandler.h b/lld/lib/ReaderWriter/MachO/ArchHandler.h
index 120f5df..712da7c 100644
--- a/lld/lib/ReaderWriter/MachO/ArchHandler.h
+++ b/lld/lib/ReaderWriter/MachO/ArchHandler.h
@@ -92,6 +92,10 @@
   /// __eh_frame.
   virtual Reference::KindValue unwindRefToEhFrameKind() = 0;
 
+  /// Returns a pointer sized reference kind.  On 64-bit targets this will
+  /// likely be something like pointer64, and pointer32 on 32-bit targets.
+  virtual Reference::KindValue pointerKind() = 0;
+
   virtual const Atom *fdeTargetFunction(const DefinedAtom *fde);
 
   /// Used by normalizedFromAtoms() to know where to generated rebasing and