Add libctb to the list of libraries to build

It will not be downloaded nor built with the current configuration.
Thanks to Curt, WE7U on the codec2 mailing list for discovering this one.


git-svn-id: https://svn.code.sf.net/p/freetel/code/fdmdv2@1311 01035d8c-6547-0410-b346-abe4f91aad63