[JENKINS-54566] Reproducing warning sometimes from FileLogStorageTest.

Author: jglick

src/test/java/org/jenkinsci/plugins/workflow/log/LogStorageTestBase.java

@@ -152,6 +152,7 @@ protected static void close(TaskListener listener) throws Exception {
         VirtualChannel channel = r.createOnlineSlave().getChannel();
         channel.call(new RemotePrint("overall from agent", overall));
         channel.call(new RemotePrint("step from agent", step));
+        channel.call(new GC());
         overallPos = assertOverallLog(overallPos, "overall from agent\n<span class=\"pipeline-node-1\">step from agent\n</span>", true);
         stepPos = assertStepLog("1", stepPos, "step from agent\n", true);
         assertEquals(overallPos, assertOverallLog(overallPos, "", true));
@@ -173,6 +174,13 @@ private static final class RemotePrint extends MasterToSlaveCallable<Void, Excep
             return null;
         }
     }
+    private static final class GC extends MasterToSlaveCallable<Void, Exception> {
+        @Override public Void call() throws Exception {
+            System.gc();
+            System.runFinalization();
+            return null;
+        }
+    }
 
     /**
      * Checks what happens when code using {@link TaskListener#getLogger} prints a line with inadequate synchronization.