Mark liblatinime_unittests as unit_test:true to run in presubmit in CI

This will ensure that the target stays green.
Note: we will clean up the explicit unit_tests:true once cc_test default is changed.

Change-Id: I5153ca918e94b370b1f08289118877d209385ba2
Test: presubmit
Bug: 180014759

native/jni/Android.bp

@@ -179,7 +179,9 @@ cc_library_static {
 cc_test {
     name: "liblatinime_unittests",
     host_supported: true,
-
+    test_options: {
+        unit_test: true,
+    },
     cflags: [
         "-Wno-unused-parameter",
         "-Wno-unused-function",