recipes: Use props for LUCI project list

Use properties for the LUCI project list instead of hardcoding
"pigweed". This will allow us to use tryjobs on internal projects on
recipes-with-led-internal.

Bug: 552
Change-Id: If6f955116279b95ce9b1d2c0b2215a0e717d771c
Reviewed-on: https://pigweed-review.googlesource.com/c/infra/recipes/+/68083
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Oliver Newman <olivernewman@google.com>
diff --git a/recipes/recipes.proto b/recipes/recipes.proto
index 028ad80..a0f3973 100644
--- a/recipes/recipes.proto
+++ b/recipes/recipes.proto
@@ -25,4 +25,7 @@
 
   // Include private tryjobs.
   bool include_private = 3;
+
+  // LUCI projects to scan for tryjobs.
+  repeated string projects = 4;
 }
diff --git a/recipes/recipes.py b/recipes/recipes.py
index d2a30b3..2c5148c 100644
--- a/recipes/recipes.py
+++ b/recipes/recipes.py
@@ -106,7 +106,7 @@
 def RunSteps(api, props):
     api.checkout()
 
-    api.recipe_testing.projects = ('pigweed',)
+    api.recipe_testing.projects = tuple(props.projects) or ('pigweed',)
 
     with api.step.defer_results():
         api.recipe_testing.run_lint(