Bazel: Remove iteration over depset

This change removes last remaining occurrences of iterations over
depsets and makes build tool chain forward compatible.

This is needed because future bazel versions are going to remove the
support for iteration over depset.

Test Plan:

  $ bazel test --incompatible_depset_is_not_iterable //...

Bug: Issue 10888
Change-Id: I9ba0403c0d86f1bc2dbd1f5daf20b96a5d63c337
diff --git a/tools/bzl/js.bzl b/tools/bzl/js.bzl
index f16bc89..ee96cce 100644
--- a/tools/bzl/js.bzl
+++ b/tools/bzl/js.bzl
@@ -312,7 +312,7 @@
         ctx.outputs.html.path + ".vulcanized.html",
     )
     destdir = ctx.outputs.html.path + ".dir"
-    zips = [z for d in ctx.attr.deps for z in d.transitive_zipfiles]
+    zips = [z for d in ctx.attr.deps for z in d.transitive_zipfiles.to_list()]
 
     hermetic_npm_binary = " ".join([
         "python",