Fix tmpfile(3).

This could be better, but at least now it works.

Change-Id: I88b7cf3f7ce8e5fa0b3fe678b7d1679a68ffffc9
diff --git a/tests/Android.mk b/tests/Android.mk
index be47585..38f8ceb 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -22,6 +22,7 @@
     getcwd_test.cpp \
     pthread_test.cpp \
     regex_test.cpp \
+    stdio_test.cpp \
     string_test.cpp \
     stubs_test.cpp \