SL-18837: On Windows, LLLeap partial final line test failed.

Add DEBUG log output to try to diagnose.

indra/llcommon/llleap.cpp

@@ -376,6 +376,17 @@ class LLLeapImpl: public LLLeap
             // Read all remaining bytes and log.
             LL_INFOS("LLLeap") << mDesc << ": " << rest << LL_ENDL;
         }
+        /*--------------------------- diagnostic ---------------------------*/
+        else if (data["eof"].asBoolean())
+        {
+            LL_DEBUGS("LLLeap") << mDesc << " ended, no partial line" << LL_ENDL;
+        }
+        else
+        {
+            LL_DEBUGS("LLLeap") << mDesc << " (still running, " << childerr.size()
+                                << " bytes pending)" << LL_ENDL;
+        }
+        /*------------------------- end diagnostic -------------------------*/
         return false;
     }