Adding Google benchmarking library.

third_party/google_benchmark/cmake/gnu_posix_regex.cpp

Index: third_party/google_benchmark/cmake/gnu_posix_regex.cpp
diff --git a/third_party/google_benchmark/cmake/gnu_posix_regex.cpp b/third_party/google_benchmark/cmake/gnu_posix_regex.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b5b91cdab7c2a383afccc2b63ddc4bd98aa64bc4
--- /dev/null
+++ b/third_party/google_benchmark/cmake/gnu_posix_regex.cpp
@@ -0,0 +1,12 @@
+#include <gnuregex.h>
+#include <string>
+int main() {
+  std::string str = "test0159";
+  regex_t re;
+  int ec = regcomp(&re, "^[a-z]+[0-9]+$", REG_EXTENDED | REG_NOSUB);
+  if (ec != 0) {
+    return ec;
+  }
+  return regexec(&re, str.c_str(), 0, nullptr, 0) ? -1 : 0;
+}
+