Fix typo in allowStderrMessages

Change-Id: Ib39ad315b0308c3d3f1b888ec08099913f71f5f9
diff --git a/src/test/java/com/android/tools/r8/TestCompilerBuilder.java b/src/test/java/com/android/tools/r8/TestCompilerBuilder.java
index 5f0843f..9ae6569 100644
--- a/src/test/java/com/android/tools/r8/TestCompilerBuilder.java
+++ b/src/test/java/com/android/tools/r8/TestCompilerBuilder.java
@@ -346,7 +346,7 @@
   }
 
   public T allowStderrMessages() {
-    allowStdoutMessages = true;
+    allowStderrMessages = true;
     return self();
   }