Add option to build UDF test libs in copy-udfs-udas.sh

The option is off by default, but useful for running this script
without building the world.

Change-Id: I82d8251cf9bb2763ce69094da1995a4d6ceff167
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2647
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins