ART: Add debug output to 063-process-manager

Add stack trace to output when we find the reaper in an unexpected
state.

Bug: 2310700
Test: art/test/testrunner/testrunner.py -b --host -t 063
Change-Id: I3abfff9c7f0d0dd02ccb5d95e737f7675723bb87
diff --git a/test/063-process-manager/src/Main.java b/test/063-process-manager/src/Main.java
index e31a0df..6cb5949 100644
--- a/test/063-process-manager/src/Main.java
+++ b/test/063-process-manager/src/Main.java
@@ -31,7 +31,13 @@
             Thread t = entry.getKey();
             String name = t.getName();
             if (name.indexOf("process reaper") >= 0) {
-                System.out.println("process manager: " + t.getState());
+                Thread.State state = t.getState();
+                System.out.println("process manager: " + state);
+                if (state != Thread.State.RUNNABLE && state != Thread.State.TIMED_WAITING) {
+                    for (StackTraceElement e : entry.getValue()) {
+                        System.out.println("  " + e);
+                    }
+                }
                 found = true;
             }
         }