Add a tiny hint for bob at the moment

Change-Id: I3da2ae662e3da96f8d76d32cdfafe6002112b758
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/71207
Reviewed-by: Adam Langley <agl@google.com>
Auto-Submit: Bob Beck <bbe@google.com>

main.star

diff --git a/main.star b/main.star
index 10b84da..3f564ca 100755
--- a/main.star
+++ b/main.star
@@ -14,6 +14,8 @@
 )
 
 REPO_URL = "https://boringssl.googlesource.com/boringssl"
+
+# The default recipe is "boringssl.py"
 RECIPE_BUNDLE = "infra/recipe_bundles/chromium.googlesource.com/chromium/tools/build"
 
 luci.project(