Fix -Wunused-vairable on release build, NFC

Author: hokein

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -4949,8 +4949,8 @@ OpenMPIRBuilder::createAtomicRead(const LocationDescription &Loc,
   if (!updateToLocation(Loc))
     return Loc.IP;
 
-  Type *XTy = X.Var->getType();
-  assert(XTy->isPointerTy() && "OMP Atomic expects a pointer to target memory");
+  assert(X.Var->getType()->isPointerTy() &&
+         "OMP Atomic expects a pointer to target memory");
   Type *XElemTy = X.ElemTy;
   assert((XElemTy->isFloatingPointTy() || XElemTy->isIntegerTy() ||
           XElemTy->isPointerTy()) &&