Fix the build after 8ac7210 made TTI mandatory

Author: d0k

llvm/include/llvm/CodeGen/SelectionDAGISel.h

@@ -57,9 +57,7 @@ class SelectionDAGISel {
   AssumptionCache *AC = nullptr;
   GCFunctionInfo *GFI = nullptr;
   SSPLayoutInfo *SP = nullptr;
-#if !defined(NDEBUG) && LLVM_ENABLE_ABI_BREAKING_CHECKS
   TargetTransformInfo *TTI = nullptr;
-#endif
   CodeGenOptLevel OptLevel;
   const TargetInstrInfo *TII;
   const TargetLowering *TLI;