Building Gforth for Apple's new Arm-based Macs

[Craig Treleaven]

Hi:

I contribute a little to the MacPorts project.  MacPorts packages many, many 
open source software titles for use on Macintosh.  I noticed that Gforth failed 
to build on our new buildbot running on an M1 machine(aka Apple’s 64 bit ARM 
SOC).  The configure phase reported the following error:

checking build system type... Invalid configuration `arm64-apple-darwin20.1.0': 
machine `arm64-apple' not recognized
configure: error: /bin/sh ./config.sub arm64-apple-darwin20.1.0 failed

For a number of years, we’ve invoked configure thusly on Intel 64 bit-based 
Macs:

./configure --prefix=/opt/local --build=x86_64-apple-darwin14.5.0 

I browsed through configure.ac but I have only a rudimentary knowledge of auto 
tools and couldn’t determine if the “-build” flag was even necessary; let alone 
if there were values I could feed to it on an arm64 Mac that would make it 
happy.

Can anyone help?

Incidentally, MacPorts tries to support even very old Macintosh systems 
including PPC (both 32 and 64 bit) as well as Intel i386 and X86_64.  With 
arm64 added to the mix, that is up to 5 archs!

If you are curious, the following is our page for Gforth on MacPorts:

https://ports.macports.org/port/gforth/summary

Craig