make(1) has a built-in variable MACHINE_ARCH that defaults to the value
of sysctl hw.machine_arch. This is not correct when building packages
under qemu. In that case poudriere sets MACHINE_ARCH in its make.conf.
Since commit d7511b9d00 make.conf is not picked up by make during
build so pass MACHINE_ARCH through the environment.
This affects building kmod ports under qemu.
This is a workaround for make not looking at UNAME_p when setting
MACHINE_ARCH. It does look at UNAME_m when setting MACHINE.
PR: 281674
Reported by: jrtc27
Exp-run by: antoine
Approved by: portmgr (antoine)
3154506a16