Modernise code to use override specifier

Generated by clang-tidy.

Test: m checkbuild
Change-Id: I8e23da6b8af31b291be2eefe9937ca222ea8a8c3
diff --git a/benchmarks/semaphore_benchmark.cpp b/benchmarks/semaphore_benchmark.cpp
index ba89137..cf51489 100644
--- a/benchmarks/semaphore_benchmark.cpp
+++ b/benchmarks/semaphore_benchmark.cpp
@@ -80,7 +80,7 @@
 
 class SemaphoreFixture : public benchmark::Fixture {
  public:
-  void SetUp(const benchmark::State&) {
+  void SetUp(const benchmark::State&) override {
     sem_init(&semaphore, 0, 0);
 
     pthread_attr_t attr;
@@ -100,7 +100,7 @@
     setup = true;
   }
 
-  ~SemaphoreFixture() {
+  ~SemaphoreFixture() override {
     if (setup) {
       // Only do this if the test was actually run.
       sched_setscheduler(0, SCHED_OTHER, &param);