How is MACHINE_ARCH dervived by make?

[Sean Bruno]

On Wed, 2014-11-26 at 13:41 -0800, Garrett Cooper wrote:
> On Nov 26, 2014, at 13:37, Sean Bruno <sbruno at ignoranthack.me> wrote:
> 
> > I have yet to find the magic bit in the build sys that causes ports to
> > go off and think that I'm building for amd64.  Building on a real amd64
> > box inside of an emulated jail via qemu and I still am getting tripped
> > up by something in our system thinking that I want amd64 as the
> > MACHINE_ARCH.
> 
> 	It’s handled in bmake/make. If you need to crossbuild, you’ll probably need to tell make what your MACHINE_ARCH/MACHINE is.
> 	Please refer to the manpages for more details.
> Cheers!
> 

Hrm, man make doesn't bring up the bmake man page (on current).  If it
*did* I would have seen the MACHINE_ARCH comments that allow overrides.
Odd.

> $ grep -rl MACHINE_ARCH contrib/bmake/ usr.bin/make | grep '\.c$'
> contrib/bmake/main.c
> contrib/bmake/arch.c
> usr.bin/make/main.c
> 

Looking now ... it sort of looks like there is some shell script hackery
to do this at build time that depends on uname in machine.sh and os.sh

sean