FindTcl and friends: no way to specify a location...
If there are multiple Tcl/Tk installations in a system (i.e. a 32-bit & 64-bit), there is no way to tell cmake (3.9) which one to use. If you define TCL_INCLUDE_PATH_PARENT, there is some success (the correct tclsh.exe * include dirs are found). But there is no way to get the correct libraries. Defining TCL_LIBRARY_PATH_PARENT does not work. At least under windows, it always get the Tcl installation installed last (that has overwritten the registry keys)