Fix -Wunused-but-set-variable in hphp/

Summary:
#buildsonlynotests - No runtime effects!

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ig-no-test - Doesn't require Instagram testing.

allow-large-files

Reviewed By: dmm-fb

Differential Revision: D62756783

fbshipit-source-id: 2e341b3690d9f8465ff88dc760cd56db215392c1

hphp/runtime/vm/jit/region-selection.cpp

@@ -1132,10 +1132,8 @@ bool check(const RegionDesc& region, std::string& error) {
  auto& blocks = region.blocks();
  for (unsigned i = 0; i < blocks.size(); i++) {
  auto bid = blocks[i]->id();
- DEBUG_ONLY unsigned nAllPreds = region.preds(bid).size();
  unsigned nVisited = 0;
  if (auto prevRetrans = region.prevRetrans(bid)) {
- nAllPreds++;
  nVisited += visited.count(prevRetrans.value());
  }
  for (auto pred : region.preds(bid)) {