if(CMAKE_CL_64) #CMAKE的内建变量，如果是true，就说明编译器的64位的，自然可以编译64bit的程序
set(ADDRESS_MODEL 64)
set(NODE_TARGET x64)
else()
set(ADDRESS_MODEL 32)
set(NODE_TARGET x86)
endif()
看以上代码，判断下就行了
CMAKE_CL_64内建的这个变量，官方文档给出来的解释是：
Using the 64 bit compiler from Microsoft
Set to true when using the 64 bit cl compiler from Microsoft.
###############update####################
如果是GCC编译器或者其他的诸如sun Studio之类的，可以设置CFLAGS CXXFLAGS变量，加入-m32 或者-m64来编译x86或者x64的程序。
如果是windows平台下VS的project文件的话，请使用VS generator，cmake -G "Visual Studio 10 Win64"就是编译为x64，cmake -G "Visual Studio 10 "就是编译为x86.
如果是Mac OS X上，使用CMAKE_OSX_ARCHITECTURES这个CMAKE的内建变量。
-
cmake -DCMAKE_OSX_ARCHITECTURES=i386 /path/to/source/dir------编译为32位cmake -DCMAKE_OSX_ARCHITECTURES=x86_64 /path/to/source/dir------编译为64位cmake "-DCMAKE_OSX_ARCHITECTURES=x86_64;i386" /path/to/source/dir-------编译为通用8664架构和i386架构的二进制
或者可以用另外一种方式，思路是这样的，其实编译为x86或者x64，本质上都是向linker传递特定的参数。如果是VS,或者是NMake的Makefiles的话，直接使用CMAKE内建的变量CMAKE_EXE_LINKER_FLAGS,来设置链接器的参数。VS toolchain 可以这样 set(CMAKE_EXE_LINKER_FLAGS "/machine:x86")。
这个变量官方给出来的解释是：
Linker flags to be used to create executables.
These flags will be used by the linker when creating an executable.
以下是构建一个console的demo：
1 SET(PROJECT_NAME dls_test) 2 3 PROJECT(${PROJECT_NAME}) 4 5 CMAKE_MINIMUM_REQUIRED(VERSION 2.8) 6 7 #ADD_DEFINITIONS(-DUNICODE -D_UNICODE) 8 ADD_DEFINITIONS(-D_CONSOLE) 9 10 11 SET(CMAKE_MFC_FLAG 1) #0: Use Standard Windows Libraries 1: Use MFC in a Static Library 2: Use MFC in a Shared DLL 12 13 14 include_directories(${PROJECT_SOURCE_DIR}) 15 include_directories(${PROJECT_SOURCE_DIR}/../inc) 16 include_directories(${PROJECT_SOURCE_DIR}/../wlp_adapter) 17 include_directories(${PROJECT_SOURCE_DIR}/../include) 18 19 LINK_DIRECTORIES(${PROJECT_SOURCE_DIR}/../lib) 20 #LINK_DIRECTORIES(${CMAKE_BINARY_DIR}/lib) 21 22 file(GLOB SRC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} main.cpp ) 23 source_group("src" FILES ${SRC}) 24 25 file(GLOB hdrs RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} *.h) 26 source_group("include" FILES ${hdrs}) 27 28 ADD_EXECUTABLE(${PROJECT_NAME} ${SRC} ${hdrs}) 29 30 if(WIN32) 31 if(CMAKE_BUILD_TYPE MATCHES "Debug") 32 #set(OPENCV_LIB "opencv_core246d.lib" "opencv_highgui246d.lib" "opencv_imgproc246d.lib" IlmImfd.lib Comctl32.lib) 33 TARGET_LINK_LIBRARIES(${PROJECT_NAME} wlp_adapter.lib hal.lib cbs.lib libglog_staticd.lib ) 34 else() 35 TARGET_LINK_LIBRARIES(${PROJECT_NAME} wlp_adapter.lib hal.lib cbs.lib libglog_static.lib ) 36 endif() 37 38 39 set_target_properties(${PROJECT_NAME} PROPERTIES LINK_FLAGS "/SUBSYSTEM:CONSOLE") 40 41 else() 42 43 TARGET_LINK_LIBRARIES(${PROJECT_NAME} wlp_adapter hal cbs glog pthread gomp rt glib-2.0 dl GL boost_system boost_filesystem boost_program_options boost_regex) 44 45 endif() 46 47 if(WIN32) 48 else() 49 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x -fPIC ") 50 endif() 51 52 set(CompilerFlags 53 CMAKE_CXX_FLAGS 54 CMAKE_CXX_FLAGS_DEBUG 55 CMAKE_CXX_FLAGS_RELEASE 56 CMAKE_C_FLAGS 57 CMAKE_C_FLAGS_DEBUG 58 CMAKE_C_FLAGS_RELEASE 59 ) 60 foreach(CompilerFlag ${CompilerFlags}) 61 string(REPLACE "/MD" "/MT" ${CompilerFlag} "${${CompilerFlag}}") 62 string(REPLACE "/Ob0" "" ${CompilerFlag} "${${CompilerFlag}}") 63 string(REPLACE "/TC" "" ${CompilerFlag} "${${CompilerFlag}}") 64 endforeach() 65 66 67 INSTALL(TARGETS ${prj_name} 68 RUNTIME DESTINATION bin 69 LIBRARY DESTINATION lib 70 ARCHIVE DESTINATION lib 71 ) 72 73 install(DIRECTORY ${PROJECT_SOURCE_DIR} 74 DESTINATION "." 75 )
reference：
http://stackoverflow.com/questions/5334095/cmake-multiarchitecture-compilation
http://blog.csdn.net/wh_xiexing/article/details/18301923
http://www.cmake.org/cmake/help/v3.0/variable/CMAKE_CL_64.html
http://www.cmake.org/cmake/help/v3.0/variable/CMAKE_EXE_LINKER_FLAGS.html