MC/ObjectWriter: Add a new IsSymbolRefDifferenceFullyResolved target format specific hook.
 - Currently just has stub implementations for Mach-O, ELF, and COFF.

llvm-svn: 122037
diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index d050ef0..e12daa7 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -1123,6 +1123,12 @@
                        UndefinedSymbolData);
   }
 
+  bool IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
+                                          const MCSymbolRefExpr *A,
+                                          const MCSymbolRefExpr *B) const {
+    return false;
+  }
+
   bool IsFixupFullyResolved(const MCAssembler &Asm,
                             const MCValue Target,
                             bool IsPCRel,