nmap: opportunistic use of libssh2

[i0ntempest]

nmap seem to link libssh2 if it's present on the system, but the dependency is not declared in the portfile:

$ otool -L /opt/local/bin/nmap
/opt/local/bin/nmap:
	/opt/local/lib/libpcre.1.dylib (compatibility version 4.0.0, current version 4.13.0)
	/opt/local/lib/libpcap.A.dylib (compatibility version 1.0.0, current version 1.10.1)
	/opt/local/lib/libssh2.1.dylib (compatibility version 2.0.0, current version 2.1.0)
	/opt/local/libexec/openssl11/lib/libssl.1.1.dylib (compatibility version 1.1.0, current version 1.1.0)
	/opt/local/libexec/openssl11/lib/libcrypto.1.1.dylib (compatibility version 1.1.0, current version 1.1.0)
	/opt/local/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.11)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1311.0.0)
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 1200.3.0)

Should probably add a libssh2 variant.

[danielluke (Daniel J. Luke)]

I think just adding libssh2 as a dependency is the right answer here, I'll check in an update shortly.

[danielluke (Daniel J. Luke)]

fixed in ​https://github.com/macports/macports-ports/commit/4461aace881af9fca572c8573640528c3c70391c