Fix unused variable from r240792.

The variable 'I' wasn't used when assertions were disabled.
This commit ensures that 'I' is used outside of an assert.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240797 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MIRPrinter.cpp

@@ -90,6 +90,7 @@ void MIRPrinter::print(const MachineFunction &MF) {
     // map back to the correct MBBs when parsing the output.
     assert(MBB.getNumber() == I++ &&
            "Can't print MBBs that aren't sequentially numbered");
+    (void)I;
     yaml::MachineBasicBlock YamlMBB;
     convert(YamlMBB, MBB);
     YamlMF.BasicBlocks.push_back(YamlMBB);