Build our benchmarks against glibc too.

Bug: 18556607
Change-Id: I455ac8b93c0835836180e549486bc52d393ee6a6
diff --git a/benchmarks/time_benchmark.cpp b/benchmarks/time_benchmark.cpp
index 22f6e8e..f093ec1 100644
--- a/benchmarks/time_benchmark.cpp
+++ b/benchmarks/time_benchmark.cpp
@@ -16,7 +16,9 @@
 
 #include "benchmark.h"
 
+#include <unistd.h>
 #include <sys/syscall.h>
+#include <sys/time.h>
 #include <time.h>
 
 static void BM_time_clock_gettime(int iters) {