[msan] Replace 8 by kShadowTLSAlignment

[eugenis]

LGTM

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

for (auto ArgIt = CB.arg_begin(), End = CB.arg_end(); ArgIt != End;
         if (Cst && Cst->isNullValue()) ArgIsInitialized = true;
       }
       if (MS.TrackOrigins && !ArgIsInitialized)
         IRB.CreateStore(getOrigin(A),
                         getOriginPtrForArgument(A, IRB, ArgOffset));
       (void)Store;
       assert(Size != 0 && Store != nullptr);
       LLVM_DEBUG(dbgs() << "  Param:" << *Store << "\n");
-      ArgOffset += alignTo(Size, 8);
+      ArgOffset += alignTo(Size, kShadowTLSAlignment);
     }
     LLVM_DEBUG(dbgs() << "  done with call args\n");
 
     FunctionType *FT = CB.getFunctionType();
     if (FT->isVarArg()) {
       VAHelper->visitCallBase(CB, IRB);
     }