setup.sh: make it resilient for dpkg lock issue
setup.sh: make it resilient for dpkg lock issue

When booting Raspbian Stretch Lite on a Raspberry Pi Zero Wireless, setup.sh
reproducibly fail to run the apt-get commands because the image now runs apt-get
very early by default. Change do_apt to retry, which works after a few cycles.

Stop installing git by default, only install it if installing golang or building
it from source.

periph/bootstrap,periph/bootstrap