[PATCH modular 3/4] build.sh: comment the supported systems and how they are detected

[Mark Kettenis]

> From: Gaetan Nadon <memsize at videotron.ca>
> Date: Sun, 02 Jan 2011 15:20:06 -0500
> 
> The term amd64 is widely used, but is only returned as a uname -m value
> by a CYGWIN system - if I understand this file correctly!
> 
>     amd64:CYGWIN*:*:* | x86_64:CYGWIN*:*:*)
> 	echo x86_64-unknown-cygwin
> 	exit ;;
> 
> On Solaris, uname -m would return x86_64 but never amd64, right?

On OpenBSD/amd64 uname -m returns amd64, which is then canonicalized
by config.sub to x86_64.  I believe FreeBSD does the same.