Ensure runsc is uploaded.

One would reasonably assume that a field named "regex" would expect
a regular expression. However, in this case, one would be wrong.

The "regex" field actually requires "FileSet" [1] syntax.

?\_(?)_/?

[1] http://ant.apache.org/manual/Types/fileset.html

PiperOrigin-RevId: 271917356

kokoro/build.cfg

@@ -16,6 +16,7 @@ env_vars {
 
 action {
   define_artifacts {
+    regex: "**/runsc"
     regex: "**/runsc.*"
     regex: "**/dists/**"
   }