remove unused variable

Change-Id: I9caad876c985482f74291e1ac2b144d31b11347a
diff --git a/recipe_modules/build/api.py b/recipe_modules/build/api.py
index 1181e28..a98e630 100644
--- a/recipe_modules/build/api.py
+++ b/recipe_modules/build/api.py
@@ -1245,7 +1245,6 @@
     Returns:
       A boolean indicating whether blobstats completed successfully.
     """
-    platform_dirname = '%s-x%d' % (self.m.platform.name, self.m.platform.bits)
     root_dir = build_results.checkout_root
 
     dart_binary_path = build_results.tool('dart')