install rpi-source for gcc-4.9 build

note.sh

sudo wget https://raw.githubusercontent.com/notro/rpi-source/master/rpi-source -O /usr/bin/rpi-source && sudo chmod +x /usr/bin/rpi-source && /usr/bin/rpi-source -q --tag-update

# check required gcc version
cat /proc/version

# install gcc 4.9
sudo apt update -y
sudo apt-get install gcc-4.9 g++-4.9 -y
update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 50
update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 20
update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.9 50
update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-6 20

#install build essential
sudo apt-get install bc libncurses5-dev -y

# install rpi-source
rpi-source