title: Generating 32-bit/64-bit Eclipse CDT projects using CMake
body: <p>I'm setting up a C++ project which will be built for 32-bit and 64-bit versions of Windows and Ubuntu.  I'm using CMake 2.8.4 and, after having played with it for a few hours, got the VS2010 32-bit and 64-bit projects set up.  The problem I ran into is that the generator for Eclipse on the Ubuntu side (technically for Eclipse generators on all platforms), doesn't have separate versions for 32-bit/64-bit.</p>
  
  <p>I realize that there's a GCC compiler switch to indicate which bit type you want (-m32, -m64) and I don't mind having separate solutions, but when I'm running cmake in the build directories, how do I tell it which one I want?  If there is no built-in way, is it possible to pass a custom variable/value, like <code>BITTYPE=64</code>, to the cmake command?  That way I could handle the rest in the CMakeLists.txt file with a simple if/else.</p>