Add documentation for cfg = "target".

PiperOrigin-RevId: 154441586

site/versions/master/docs/skylark/rules.md

diff --git a/site/versions/master/docs/skylark/rules.md b/site/versions/master/docs/skylark/rules.md
index 56ef328..c730c84 100644
--- a/site/versions/master/docs/skylark/rules.md
+++ b/site/versions/master/docs/skylark/rules.md
@@ -290,7 +290,7 @@
 For each [label attribute](lib/attr.html#label), you can decide whether the
 dependency should be built in the same configuration, or transition to the host
 configuration (using `cfg`). If a label attribute has the flag
-`executable=True`, the configuration must be set explictly.
+`executable=True`, the configuration must be set explicitly.
 [See example](cookbook.html#execute-a-binary)
 
 In general, sources, dependent libraries, and executables that will be needed at
@@ -300,6 +300,10 @@
 should be built for the host configuration. In this case, specify `cfg="host"`
 in the attribute.
 
+Otherwise, executables that are used at runtime (e.g. as part of a test) should
+be built for the target configuration. In this case, specify `cfg="target"` in
+the attribute.
+
 The configuration `"data"` is present for legacy reasons and should be used for
 the `data` attributes.