Add a debug log for tests that aren't eligible for the roboleaf mode.

This helps to figure out why atest gracefully fell back to standard
atest for command lines that have more than 1 test target.

Test: m atest && atest-dev adbd_test foo_test

Change-Id: I59d4e1dfd6cf3ef03cd526b4d7ceda9d59a87a36
diff --git a/atest/test_runners/roboleaf_test_runner.py b/atest/test_runners/roboleaf_test_runner.py
index dfb103d..d06a8f2 100644
--- a/atest/test_runners/roboleaf_test_runner.py
+++ b/atest/test_runners/roboleaf_test_runner.py
@@ -104,6 +104,10 @@
         # mode.
         return eligible_tests
 
+    logging.debug(
+        "roboleaf-mode: [%s] are not eligible for b test.",
+        ", ".join(set(tests).difference(eligible_tests.keys())))
+
     # Gracefully fall back to standard atest if not every test is b testable.
     return {}