FTL: Add invariant for non-null pointers

Upcasting is not supported for now.

Bug: 185536303
Test: ftl_test
Change-Id: Id37d3e9a4a794291417405eb2a8a300a9d2bfe72
diff --git a/libs/ftl/Android.bp b/libs/ftl/Android.bp
index c1945fd..81113bc 100644
--- a/libs/ftl/Android.bp
+++ b/libs/ftl/Android.bp
@@ -22,6 +22,7 @@
         "flags_test.cpp",
         "future_test.cpp",
         "match_test.cpp",
+        "non_null_test.cpp",
         "optional_test.cpp",
         "small_map_test.cpp",
         "small_vector_test.cpp",