[benchmark] getloadavg not supported under uclibc-ng.

[lancethepants]

Summary

The uclibc-ng standard library does not support getloadavg so we stub it out along with android.

[lancethepants]

Going to see about adding getloadavg to upstream uclibc-ng first so hold on this.

[lancethepants]

I did get this upstreamed so this patch no longer needed.
https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/?id=ad3a130dad88ad7a59dcd965b0cf9bd0d713595e

third-party/benchmark/src/sysinfo.cc

#endif
   SleepForMilliseconds(estimate_time_ms);
   return static_cast<double>(cycleclock::Now() - start_ticks);
 }
 
 std::vector<double> GetLoadAvg() {
 #if (defined BENCHMARK_OS_FREEBSD || defined(BENCHMARK_OS_LINUX) ||     \
      defined BENCHMARK_OS_MACOSX || defined BENCHMARK_OS_NETBSD ||      \
      defined BENCHMARK_OS_OPENBSD || defined BENCHMARK_OS_DRAGONFLY) && \
-    !defined(__ANDROID__)
+    !defined(__ANDROID__) && !defined(__UCLIBC__)
   constexpr int kMaxSamples = 3;
   std::vector<double> res(kMaxSamples, 0.0);
   const int nelem = getloadavg(res.data(), kMaxSamples);
   if (nelem < 1) {
     res.clear();
   } else {
     res.resize(nelem);
   }