Add trivial no-op <nl_types.h>.

Needed to build OpenMP.

Bug: http://b/27617302
Change-Id: Iac15c84ead6f5d5274cfdb2d6d4a4ec0072244bb
diff --git a/tests/Android.mk b/tests/Android.mk
index c7356b8..7292d9d 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -74,6 +74,7 @@
     net_if_test.cpp \
     netinet_in_test.cpp \
     netinet_udp_test.cpp \
+    nl_types_test.cpp \
     pthread_test.cpp \
     pty_test.cpp \
     regex_test.cpp \