compiling 5.1.2 kernel for amd64 on i386?

[Malcolm Herbert <mjch%mjch.net@localhost>]

What's the best way to get a 5.1.2 amd64 kernel compiled when I only
have an i386 host to work on?

I've copied and modified the kernel config within
sys/arch/amd64/conf/DEIMOS however after I run the config script and try
build.sh with the following:

  ./build.sh -u -a amd64 kernel=DEIMOS

the build.sh script complains of an unknown target MACHINE_ARCH: amd64

How can I kick this off? The target host is not capable of running a
compile as it's quite resource-starved.

Regards,
Malcolm

-- 
Malcolm Herbert                                This brain intentionally
mjch%mjch.net@localhost                                                left 
blank