Tests: never use System.err

Always print stack traces to System.out, and replace all
System.err.println()'s with System.out.println().

Follow-up of https://android-review.googlesource.com/#/c/187020/ and
https://android-review.googlesource.com/#/c/407032/.

Test: m test-art-host
      m test-art-target
Change-Id: I9ab9cd955a8db25b2ec6673790e5bc924f62c88a
diff --git a/test/138-duplicate-classes-check/src/Main.java b/test/138-duplicate-classes-check/src/Main.java
index 5ffceb9..b32f0bc 100644
--- a/test/138-duplicate-classes-check/src/Main.java
+++ b/test/138-duplicate-classes-check/src/Main.java
@@ -42,7 +42,7 @@
             Method test = testEx.getDeclaredMethod("test");
             test.invoke(null);
         } catch (Exception exc) {
-            exc.printStackTrace();
+            exc.printStackTrace(System.out);
         }
     }
 }