actually add new test

test/walltime_test.cc

+
+#include <cstddef>
+
+#include "benchmark/benchmark_api.h"
+#include "../src/walltime.h"
+
+void BM_CPUTimeNow(benchmark::State& state) {
+    while (state.KeepRunning()) {
+        benchmark::WallTime volatile now = benchmark::walltime::CPUWalltimeNow();
+        ((void)now);
+    }
+}
+BENCHMARK(BM_CPUTimeNow);
+
+void BM_ChronoTimeNow(benchmark::State& state) {
+    while (state.KeepRunning()) {
+        benchmark::WallTime volatile now = benchmark::walltime::ChronoWalltimeNow();
+        ((void)now);
+    }
+}
+BENCHMARK(BM_ChronoTimeNow);
+
+
+BENCHMARK_MAIN()