Fix zip namelist not returning the file content.

The namelist.py resource was not adding the json information to stdout.

Change-Id: I3b1198795bd9adc1593565f58835906acd08ec57
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/41580
Reviewed-by: Ricardo Amador <ricardoamador@google.com>
Commit-Queue: Godofredo Contreras <godofredoc@google.com>
(cherry picked from commit 24338c29c3da075393f34526c592a7e47e688978)
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/41702
Reviewed-by: Xilai Zhang <xilaizhang@google.com>
diff --git a/recipe_modules/zip/resources/namelist.py b/recipe_modules/zip/resources/namelist.py
index 1ab5dec..4b15da0 100644
--- a/recipe_modules/zip/resources/namelist.py
+++ b/recipe_modules/zip/resources/namelist.py
@@ -17,7 +17,7 @@
   assert os.path.isfile(zip_file), zip_file
 
   with zipfile.ZipFile(zip_file) as artifact_zip:
-    json.dumps(artifact_zip.namelist())
+    sys.stdout.write(json.dumps(artifact_zip.namelist()))
   return 0
 
 if __name__ == '__main__':