README: fix build->built typo
README: fix build->built typo

(cherry picked from commit e271fd57132763f39c6993a35e6c063aac3af4f1)

maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum,maran/go-ethereum