aarch64: a port, or a MACHINE_ARCH under evbarm?

[Greg Troxel <gdt%lexort.com@localhost>]

(As usual I'll spiff up the wiki when I become enlightened.)

There is an evbarm port, which has multiple MACHINE_ARCH subtypes (e.g
earmv7hf), and within the port there is support for a number of hardware
platforms.

It seems there is an earmv8hf hardware type, and that usually (but not
reliably always?) these cpus also implement "aarch64" in addition to the
familiar "aarch32" instrructions.

I also see NetBSD/aarch64 referred to as a port, which would imply "-a
aarch64" to build.sh.


So, for running on RPI3, or for pinebook64, or various other things,
what is the build.sh command, and which port is that.  And if the -a
value is not aarch64 but it's the aarch64 port, what does that mean?