step 1
download one version of arm-linux-gcc ，such as 4.3.2 https://download.csdn.net/download/xinhuameng/2642452
step 2
extract the downloaded files by: tar zxf arm-linux。。。。
step 3
move to /usr/local/arm/4.3.2
step 4
add environment variables " export PATH=$PATH:......bin"