fix clang-tidy warnings (#1195)

test/benchmark_random_interleaving_gtest.cc

diff --git a/test/benchmark_random_interleaving_gtest.cc b/test/benchmark_random_interleaving_gtest.cc
index f68c680..88e274e 100644
--- a/test/benchmark_random_interleaving_gtest.cc
+++ b/test/benchmark_random_interleaving_gtest.cc
@@ -34,7 +34,7 @@
   }
 };
 
-static EventQueue* queue = new EventQueue;
+EventQueue* queue = new EventQueue();
 
 class NullReporter : public BenchmarkReporter {
  public:
@@ -60,7 +60,7 @@
   }
 };
 
-static void BM_Match1(benchmark::State& state) {
+void BM_Match1(benchmark::State& state) {
   const int64_t arg = state.range(0);
 
   for (auto _ : state) {

test/perf_counters_test.cc

diff --git a/test/perf_counters_test.cc b/test/perf_counters_test.cc
index d6e0284..3017a45 100644
--- a/test/perf_counters_test.cc
+++ b/test/perf_counters_test.cc
@@ -5,7 +5,7 @@
 #include "benchmark/benchmark.h"
 #include "output_test.h"
 
-void BM_Simple(benchmark::State& state) {
+static void BM_Simple(benchmark::State& state) {
   for (auto _ : state) {
     benchmark::DoNotOptimize(state.iterations());
   }
@@ -13,7 +13,7 @@
 BENCHMARK(BM_Simple);
 ADD_CASES(TC_JSONOut, {{"\"name\": \"BM_Simple\",$"}});
 
-void CheckSimple(Results const& e) {
+static void CheckSimple(Results const& e) {
   CHECK_COUNTER_VALUE(e, double, "CYCLES", GT, 0);
   CHECK_COUNTER_VALUE(e, double, "BRANCHES", GT, 0.0);
 }

test/repetitions_test.cc

diff --git a/test/repetitions_test.cc b/test/repetitions_test.cc
index f93de50..2f94d05 100644
--- a/test/repetitions_test.cc
+++ b/test/repetitions_test.cc
@@ -6,7 +6,7 @@
 // ------------------------ Testing Basic Output --------------------------- //
 // ========================================================================= //
 
-void BM_ExplicitRepetitions(benchmark::State& state) {
+static void BM_ExplicitRepetitions(benchmark::State& state) {
   for (auto _ : state) {
   }
 }
@@ -105,7 +105,7 @@
 // ------------------------ Testing Basic Output --------------------------- //
 // ========================================================================= //
 
-void BM_ImplicitRepetitions(benchmark::State& state) {
+static void BM_ImplicitRepetitions(benchmark::State& state) {
   for (auto _ : state) {
   }
 }