[Cmake] Forcing a NOTFOUND

[Miller, James V (CRD)]

Some software projects have configured CMake to search diligently for certain libraries on your
system. 
If it finds them, it uses them for in its build process. If they are not found, the build configures
itself differently.
 
Here's my problem.  One of these projects finds a tiff library in the directory structure of another
one
of my projects (as opposed to inside a system directory).  I don't want this second system to use the

version that it found in the first.  In fact, I do not want it use one at all.