Refuse to proceed if the final argument starts with a hyphen.
Refuse to proceed if the final argument starts with a hyphen.

This detects and prevents a specific category of user error, where an
incomplete cipherscan command line ending in an OpenSSL -option results
in cipherscan attempting to scan the target '-option:443'.

PeterMosmans/cipherscan,MikeDawg/cipherscan,MikeDawg/cipherscan,MikeDawg/cipherscan,jvehent/cipherscan,jvehent/cipherscan,PeterMosmans/cipherscan,PeterMosmans/cipherscan,jvehent/cipherscan