If you have previously built EOSIO from source and now wish to install the prebuilt binaries, or to build from source again, it is recommended to run the eosio_uninstall.sh script within the eos/scripts folder:

cd ~/eosio/eos
sudo ./scripts/eosio_uninstall.sh

[[info	Uninstall Dependencies]]
	The uninstall script will also prompt the user to uninstall EOSIO dependencies. This is recommended if installing prebuilt EOSIO binaries or building EOSIO for the first time.