Context is  bug 903523 .

I see two main options.

1. Add a builder to the recipe engine CQ, similar to https://ci.chromium.org/p/infra/builders/luci.infra.try/Build%20Recipes%20Tester, which runs a chromium recipe with the recipe engine CL.

2. Make the existing builder run on changes to recipes.cfg. Currently, the recipes.py analyze command doesn't take into account changes to recipes.cfg, which is why the Build Recipes Tester does nothing when run on recipe rolls (https://ci.chromium.org/p/infra/builders/luci.infra.try/Build%20Recipes%20Tester/b8930280228017517360 is a sample recipe roll CL).

I worry about #2, because it would mean a roll would sit there for 40-ish minutes before failing, and then the author would have to revert the upstream CL, which has already rolled? Maybe those concerns aren't valid?