Add includes to fix gcc 4.7 build.

Change-Id: Idf84f156047270b81c5d10a55a3a1c96b415cddc
diff --git a/runtime/elf_file.cc b/runtime/elf_file.cc
index fac6f53..fe33806 100644
--- a/runtime/elf_file.cc
+++ b/runtime/elf_file.cc
@@ -16,6 +16,9 @@
 
 #include "elf_file.h"
 
+#include <sys/types.h>
+#include <unistd.h>
+
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "utils.h"