folly: ubsan: Benchmark: avoid division by zero (fsanitize=float-divide-by-zero)

Reviewed By: philippv

Differential Revision: D2886132

fb-gh-sync-id: a845d657fb920847df52fe5ec077e91554544f5b

folly/Benchmark.cpp

@@ -397,7 +397,9 @@ static void printBenchmarkResultsAsTable(
     s.resize(columns - 29, ' ');
     auto nsPerIter = get<2>(datum);
     auto secPerIter = nsPerIter / 1E9;
-    auto itersPerSec = 1 / secPerIter;
+    auto itersPerSec = (secPerIter == 0)
+                           ? std::numeric_limits<double>::infinity()
+                           : (1 / secPerIter);
     if (!useBaseline) {
       // Print without baseline
       printf("%*s           %9s  %7s\n",