Only run recipe simulation tests if infra/ changes.

This should lessen the need for mortals to have coverage.py,
and saves 1.8s (of 3.6s) on my desktop for this non-infra change.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2187713002

Review-Url: https://codereview.chromium.org/2187713002
1 file changed