Workaround missing std::this_thread::sleep_for function in tests.

test/benchmark_test.cc

@@ -186,9 +186,11 @@ static void BM_ManualTiming(benchmark::State& state) {
 
   while (state.KeepRunning()) {
     auto start   = std::chrono::high_resolution_clock::now();
-    // Simulate some useful workload with a sleep
-    std::this_thread::sleep_for(std::chrono::duration_cast<
-      std::chrono::nanoseconds>(sleep_duration));
+    // Simulate some useful workload by sleeping.
+    // Note: std::this_thread::sleep_for doesn't work with GCC 4.7 on some
+    // platforms.
+    const auto sleep_end = std::chrono::steady_clock::now() + sleep_duration;
+    while (std::chrono::steady_clock::now() < sleep_end) {}
     auto end     = std::chrono::high_resolution_clock::now();
 
     auto elapsed =

test/options_test.cc

@@ -11,9 +11,11 @@ void BM_basic(benchmark::State& state) {
 void BM_basic_slow(benchmark::State& state) {
   std::chrono::milliseconds sleep_duration(state.range_x());
   while (state.KeepRunning()) {
-    std::this_thread::sleep_for(
-      std::chrono::duration_cast<std::chrono::nanoseconds>(sleep_duration)
-      );
+    // Simulate some useful workload by sleeping.
+    // Note: std::this_thread::sleep_for doesn't work with GCC 4.7 on some
+    // platforms.
+    const auto sleep_end = std::chrono::steady_clock::now() + sleep_duration;
+    while (std::chrono::steady_clock::now() < sleep_end) {}
   }
 }