[SystemZ] Fix a warning

This patch fixes:

  llvm/lib/Target/SystemZ/SystemZISelLowering.cpp:953:30: error:
  unused variable 'TRI' [-Werror,-Wunused-variable]

Author: kazutakahirata

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

@@ -961,6 +961,7 @@ SystemZTargetLowering::emitEHSjLjSetJmp(MachineInstr &MI,
   Register DstReg = MI.getOperand(0).getReg();
   const TargetRegisterClass *RC = MRI.getRegClass(DstReg);
   assert(TRI->isTypeLegalForClass(*RC, MVT::i32) && "Invalid destination!");
+  (void)TRI;
   Register mainDstReg = MRI.createVirtualRegister(RC);
   Register restoreDstReg = MRI.createVirtualRegister(RC);