[CMake] Building Mac OSX .apps for Sys 10.6 and 10.8 with Cmake using 10.7.5 on the command line

[Ed]

Hello:
I am trying to build an app to be compatible with Mac OSX systems 10.6, 10.7, and 10.8 using the command line with cmake.  I have successfully built it for 10.7.5, now I would like to expand this app to be compatible with 10.6 and 10.8 is this possible?
This is the command I am issuing to cmake:
cmake -DCMAKE_OSX_64=ON -DCMAKE_C_COMPILER=/usr/bin/gcc -DCMAKE_CXX_COMPILER=/usr/bin/g++ ..

Could anyone help me to build this app to be compatible with the other two system?

TIA,
Freddie