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

Without SVN installed, running nmap 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 https://svn.nmap.org/updates is only accessible to
primary nmap developers at the moment, build nmap without nmap-update
(rather than add SVN as a dependency).

Closes #26386.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>