cmake and Subsurface builds

[Dirk Hohndel]

On Thu, Apr 16, 2015 at 10:49:44AM +0000, Tomaz Canabrava wrote:
> Take a look on the cmakelists.txt file on the source directory.
> Target_link_libraries, add that.
> 
> But that strange, it shouldnt need that.

So I had created a Ubuntu only fix for that... and then blew away the
Ubuntu install before sending the fix out. I just can't stand using Ubuntu
:-/

Doing this for all Linux versions shouldn't hurt, so let me push out a fix
that does that and see how it goes.

/D