[CMake] 32/64 bit flag

[pellegrini]

Dear CMakers,

I have to build cmake files for a Fortran project using ifort compiler 
on Windows, linux and macos platform.
That project will be linked to Winteracter Fortran library whose 
installation paths are different depending on the 32
or 64 bit versions. Is there a way to automatically detect whether the 
build is a 32 bit or 64 bit one in order to define
the correct path for Winteracter library ? Up to now, the only way I 
found to do this was by introducing a cmake
option to my build (ON for 64bit build and OFF for a 32 one). I also saw 
the CMAKE_CL_64 flag that could have been
interesting but unfortunately it is only for microsoft.

thanks for your help

Eric