Add documentation that configuration is required when attribute is executable.
--
MOS_MIGRATED_REVID=138822436
diff --git a/site/versions/master/docs/skylark/rules.md b/site/versions/master/docs/skylark/rules.md
index 809b876..cc92341 100644
--- a/site/versions/master/docs/skylark/rules.md
+++ b/site/versions/master/docs/skylark/rules.md
@@ -254,7 +254,8 @@
By default, a target is built in the target configuration. For each label
attribute, you can decide whether the dependency should be built in the same
-configuration, or in the host configuration.
+configuration, or in the host configuration. If `executable=True`, configuration
+setting is required.
In general, sources, dependent libraries, and executables that will be needed at
runtime can use the same configuration.
