Adding Google benchmarking library.

third_party/google_benchmark/src/internal_macros.h

Index: third_party/google_benchmark/src/internal_macros.h
diff --git a/third_party/google_benchmark/src/internal_macros.h b/third_party/google_benchmark/src/internal_macros.h
new file mode 100644
index 0000000000000000000000000000000000000000..ab9dd85c10238207e2c5aab7714f261b9cc27214
--- /dev/null
+++ b/third_party/google_benchmark/src/internal_macros.h
@@ -0,0 +1,55 @@
+#ifndef BENCHMARK_INTERNAL_MACROS_H_
+#define BENCHMARK_INTERNAL_MACROS_H_
+
+#include "benchmark/macros.h"
+
+#ifndef __has_feature
+#define __has_feature(x) 0
+#endif
+
+#if defined(__clang__)
+#define COMPILER_CLANG
+#elif defined(_MSC_VER)
+#define COMPILER_MSVC
+#elif defined(__GNUC__)
+#define COMPILER_GCC
+#endif
+
+#if __has_feature(cxx_attributes)
+#define BENCHMARK_NORETURN [[noreturn]]
+#elif defined(__GNUC__)
+#define BENCHMARK_NORETURN __attribute__((noreturn))
+#elif defined(COMPILER_MSVC)
+#define BENCHMARK_NORETURN __declspec(noreturn)
+#else
+#define BENCHMARK_NORETURN
+#endif
+
+#if defined(__CYGWIN__)
+#define BENCHMARK_OS_CYGWIN 1
+#elif defined(_WIN32)
+#define BENCHMARK_OS_WINDOWS 1
+#elif defined(__APPLE__)
+#include "TargetConditionals.h"
+  #if defined(TARGET_OS_MAC)
+    #define BENCHMARK_OS_MACOSX 1
+    #if defined(TARGET_OS_IPHONE)
+      #define BENCHMARK_OS_IOS 1
+    #endif
+  #endif
+#elif defined(__FreeBSD__)
+#define BENCHMARK_OS_FREEBSD 1
+#elif defined(__linux__)
+#define BENCHMARK_OS_LINUX 1
+#elif defined(__native_client__)
+#define BENCHMARK_OS_NACL 1
+#elif defined(EMSCRIPTEN)
+#define BENCHMARK_OS_EMSCRIPTEN 1
+#endif
+
+#if !__has_feature(cxx_exceptions) && !defined(__cpp_exceptions) \
+     && !defined(__EXCEPTIONS)
+#define BENCHMARK_HAS_NO_EXCEPTIONS
+#endif
+
+#endif  // BENCHMARK_INTERNAL_MACROS_H_