Add a unit test for syscall(2).

Change-Id: Ic7d9735d46711af93c3a1747de7b2eb8cebea094
diff --git a/tests/Android.mk b/tests/Android.mk
index ca6a06b..3344687 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -86,6 +86,7 @@
     sys_select_test.cpp \
     sys_sendfile_test.cpp \
     sys_stat_test.cpp \
+    sys_syscall_test.cpp \
     sys_time_test.cpp \
     system_properties_test.cpp \
     time_test.cpp \