random engine benchmark should parse CLI args

Summary: TSIA.

Differential Revision: D91149502

fbshipit-source-id: 590ff907a8e7e9dc2aa6f1de2f33fa786ca84c36

Author: yfeldblum

third-party/folly/src/folly/random/test/engine_bench.cpp

@@ -195,7 +195,8 @@ BENCHMARK(next_folly_xoshiro256pp_64, iters) {
   bm_next<rng_t>(iters);
 }
 
-int main() {
+int main(int argc, char** argv) {
+  folly::gflags::ParseCommandLineFlags(&argc, &argv, true);
   folly::runBenchmarks();
   return 0;
 }