Upgrade bazlets to latest stable-2.15

Fix genrule2 to clean up temporary folder content

Change-Id: I1d186a2082b364f7acc2d99c20ec0211efebbfd2
diff --git a/WORKSPACE b/WORKSPACE
index ff6f4ac..96f9dc7 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "ae1cd231b0262b2738e6c0593eb3c504209ad4f5",
+    commit = "9066deaedaf97c619c3de31fefae542ccfc62b7d",
     #local_path = "/home/<user>/projects/bazlets",
 )