benchmark_fixture.h: silence -Wsign-compare

Author: ftynse

tc/benchmarks/benchmark_fixture.h

@@ -65,11 +65,11 @@ struct Benchmark : public ::testing::Test {
   void SetUp() {
     if (!FLAGS_disable_version_checks) {
       auto cudnnVersion = cudnnGetVersion();
-      TC_CHECK_LE(6021, cudnnVersion)
+      TC_CHECK_LE(6021u, cudnnVersion)
           << "[CUDNN][VERSION] Enforce version compatibility check";
 
       auto cudaRtVersion = cudnnGetCudartVersion();
-      TC_CHECK_LE(8000, cudaRtVersion)
+      TC_CHECK_LE(8000u, cudaRtVersion)
           << "[CUDART][VERSION] Enforce version compatibility check";
 
       int cublasVersion;