[MC] Drop unneeded std::abs for DW_def_cfa_offset in DarwinX86AsmBackend::generateCompactUnwindEncoding

This clean-up is available after double negation bugs are fixed.

llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

@@ -1470,7 +1470,7 @@ public:
         //  L0:
         //     .cfi_def_cfa_offset 80
         //
-        StackSize = std::abs(Inst.getOffset()) / StackDivide;
+        StackSize = Inst.getOffset() / StackDivide;
         ++NumDefCFAOffsets;
         break;
       }