Build our benchmarks against glibc too.

Bug: 18556607
Change-Id: I455ac8b93c0835836180e549486bc52d393ee6a6
diff --git a/benchmarks/benchmark_main.cpp b/benchmarks/benchmark_main.cpp
index d60670b..815d56b 100644
--- a/benchmarks/benchmark_main.cpp
+++ b/benchmarks/benchmark_main.cpp
@@ -19,6 +19,7 @@
 #include <regex.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <time.h>
 
 #include <string>
 #include <map>