<span style="font-size:14px;">1. modify the variables "CMAKE_C_COMPILER" and "CMAKE_CXX_COMPILER", then you can do cross compile with cmake
for example:</span>

PROJECT(test_cmake)
SET(CMAKE_C_COMPILER   arm-linux-gnueabi-gcc)
## SET(CMAKE_CXX_COMPILER arm-linux-gnueabi-g++)
SET(SRC_LIST test1.c)
ADD_EXECUTABLE(test_cmake ${SRC_LIST})

2.  if  you want to add some flags to control compile process,  like

 gcc  test.c -o my_test   -O3   in makefile

you should modify the variables 

CMAKE_C_FLAGS and CMAKE_CXX__FLAGS in your cmake 
for example

PROJECT(test_cmake)
SET(CMAKE_C_COMPILER   arm-linux-gnueabi-gcc)
## SET(CMAKE_CXX_COMPILER arm-linux-gnueabi-g++)
SET(CMAKE_C_FLAGS “${CMAKE_C_FLAGS} -mcpu=cortex-a7 -mtune=cortex-a7 -mfpu=neon-vfpv6 -mfloat-abi=softfp”)
SET(SRC_LIST test1.c)
ADD_EXECUTABLE(test_cmake ${SRC_LIST})

reference:

http://blog.csdn.net/feibuhui123/article/details/8552719