[CMake] How to convince cmake to find Tcl/Tk 8.6?

[Georgios Petasis]

Hi all,

I am using cmake 2.8.8 under Fedora 17 64 bit, in which I have installed 
ActiveTcl 8.6 in /opt.
My path variable starts with:

/opt/ActiveTcl-8.6/bin:...

And when I run tclsh/tclsh8.6/wish/wish8.6, I get the ActiveTcl one, 
from /opt.

However, cmake does not find this Tcl/Tk installation, and locates 
instead Tcl 8.5 installed in /usr.
(Which cannot be used for compilation, since the application depends on 
8.6 features).

How can I convince cmake to pick up the 8.6 version installed in 
/opt/ActiveTcl-8.6/ ?

George