do i need to delete my current BitcoinArmory directory before building as i am getting this error:
yes. That's what it's telling you, and it means it. The other alternative is to execute the git command from a different directory, i.e. one in which no directory named BitcoinArmory exists. There is probably also a way of indicating to git that you want the target directory to have an alternative name, not sure what that is. Use "man git" or "git --help" for that.
Also, I would consider looking into using the "make install" command subsequent to make itself (perhaps specifically for Python/SWIG projects), as once you've ran make, the built application directory structure ends up in your home directory somewhere. The permissions set on those folders would allow external attackers to discover their existence, so the Armory executable & dependents are better off living in /usr/lib/ (where the Armory installer places them on Linux).