Fix the Mac libbase build.

Change-Id: I34224fa66850915ef47c88ef4c79efbc53f3f38e
diff --git a/base/logging_test.cpp b/base/logging_test.cpp
index a1e31a6..c12dfa5 100644
--- a/base/logging_test.cpp
+++ b/base/logging_test.cpp
@@ -16,6 +16,8 @@
 
 #include "base/logging.h"
 
+#include <libgen.h>
+
 #include <regex>
 #include <string>