Use `call` in recipe bundles to allow appending to the recipes.bat file.
Use `call` in recipe bundles to allow appending to the recipes.bat file.

This is in support of adding the -debug flag to led (
https://chromium-review.googlesource.com/1147926).

R=ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org

Change-Id: Ia5c24c7bd07aadabc69820365f6ec74838202cbe
Reviewed-on: https://chromium-review.googlesource.com/1147933
Reviewed-by: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>
Commit-Queue: Robbie Iannucci <40f3d43a28ebae3cb819288542e1c84d73d962d5@chromium.org>

luci/recipes-py,luci/recipes-py