MC/Mach-O/ARM: We always use the SECTDIFF reloc type on ARM, which is
esp. important given that the LOCAL_SECTDIFF enumeration got redefined.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122412 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MachObjectWriter.cpp b/lib/MC/MachObjectWriter.cpp
index b746683..cab6452 100644
--- a/lib/MC/MachObjectWriter.cpp
+++ b/lib/MC/MachObjectWriter.cpp
@@ -827,12 +827,7 @@
                           "' can not be undefined in a subtraction expression");
 
       // Select the appropriate difference relocation type.
-      //
-      // Note that there is no longer any semantic difference between these two
-      // relocation types from the linkers point of view, this is done solely
-      // for pedantic compatibility with 'as'.
-      Type = A_SD->isExternal() ? (unsigned)macho::RIT_Difference :
-        (unsigned)macho::RIT_Generic_LocalDifference;
+      Type = macho::RIT_Difference;
       Value2 = getSymbolAddress(B_SD, Layout);
       FixedValue -= getSectionAddress(B_SD->getFragment()->getParent());
     }