[CMake] Forcing CMake to never search install path

[Clifford Yapp]

I could probably "work around" the problem by making my own custom
Find* modules that checked the paths of results against the
CMAKE_INSTALL_PREFIX path, or (eek) maybe even do
find_library/_find_library wrapping to filter results globally, but
that seems like an awful hack - wouldn't it make more sense to just
add a switch to enable/disable the use of those paths in the FIND
systems?  Is there some policy on this from the Kitware guys?

On a related note, is there any debugging option that will let me see
what paths a FIND_LIBRARY command is searching in?  I'm willing to
expand my "strip the install path out of the internal variables"
approach (which does (mostly) work, despite altering variables which
are apparently supposed to be internal) if I can just figure out
what's causing Windows in particular to search more aggressively...

Cheers,
CY