- cmake升级参考：
linux手机更新cmake版本
- gcc和g 升级参考：
linux手机更新 gcc g 版本
root@ubuntu-phablet:/# gcc --version
gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
root@ubuntu-phablet:/# gcc-9 --version
gcc-9 (Ubuntu 9.4.0-1ubuntu1~16.04) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
对于c 20已经支持了（g -9）
root@ubuntu-phablet:/# g -std=c 2a
g : error: unrecognized command line option ‘-std=c 2a’
g : fatal error: no input files
compilation terminated.
root@ubuntu-phablet:/# g -9 -std=c 2a
g -9: fatal error: no input files
compilation terminated.
查看所有g 或gcc版本：
root@ubuntu-phablet:/# ls /usr/bin/g *
/usr/bin/g /usr/bin/g -5 /usr/bin/g -9
将默认g 和gcc进行调整：
root@ubuntu-phablet:/# update-alternatives --display gcc
update-alternatives: error: no alternatives for gcc
root@ubuntu-phablet:/# update-alternatives --display g
update-alternatives: error: no alternatives for g
root@ubuntu-phablet:/# update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 10
update-alternatives: using /usr/bin/gcc-5 to provide /usr/bin/gcc (gcc) in auto mode
root@ubuntu-phablet:/# update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-9 40
update-alternatives: using /usr/bin/gcc-9 to provide /usr/bin/gcc (gcc) in auto mode
root@ubuntu-phablet:/# update-alternatives --install /usr/bin/g g /usr/bin/g -5 10
update-alternatives: using /usr/bin/g -5 to provide /usr/bin/g (g ) in auto mode
root@ubuntu-phablet:/# update-alternatives --install /usr/bin/g g /usr/bin/g -9 40
update-alternatives: using /usr/bin/g -9 to provide /usr/bin/g (g ) in auto mode
root@ubuntu-phablet:/# update-alternatives --display gcc
gcc - auto mode
link best version is /usr/bin/gcc-9
link currently points to /usr/bin/gcc-9
link gcc is /usr/bin/gcc
/usr/bin/gcc-5 - priority 10
/usr/bin/gcc-9 - priority 40
root@ubuntu-phablet:/# update-alternatives --display g
g - auto mode
link best version is /usr/bin/g -9
link currently points to /usr/bin/g -9
link g is /usr/bin/g
/usr/bin/g -5 - priority 10
/usr/bin/g -9 - priority 40
再次测试：
