Add build flag '--without-nmap-update'

Running nmap without SVN installed causes it to complain that 'libsvn_client-1.0.dylib' isn't loaded, which the 'nmap-update' component depends on to connect to https://svn.nmap.org/updates to get NSE script updates.

Since it looks like '/updates' is only accessible to the primary nmap developers at the moment, build nmap without nmap-update component rather than add SVN as a dependency.