Add libwatchdog_test to native test

- libwatchdog_test is a unit test for car watchdog.
- Android Auto Embedded team want libwatchdog_test to be run as
presubmit test.

Bug: 154545474
Test: build okay
Change-Id: I80fc35901dcd32fe1b4dd337172937c3741d095b
diff --git a/build/tasks/tests/native_test_list.mk b/build/tasks/tests/native_test_list.mk
index 7117f2a..b1565ec 100644
--- a/build/tasks/tests/native_test_list.mk
+++ b/build/tasks/tests/native_test_list.mk
@@ -131,3 +131,7 @@
     SurfaceFlinger_test \
     lmkd_unit_test \
     vrflinger_test
+
+ifeq ($(BOARD_IS_AUTOMOTIVE), true)
+native_tests += libwatchdog_test
+endif