On amd64, emulators/linux_base-8 cannot be built with the following error,
in case a separate make process is executed 
(when installed by, for example, 'make reinstall' or portupgrade).

    ===>  Installing for linux_base-8-8.0_6
    kern.fallback_elf_brand: -1 -> 3
    redhat-release-8.0-8.noarch.rpm
    glibc-common-2.3.2-4.80.8.i386.rpm
    ELF binary type "0" not known.
    execution of glibc-common-2.3.2-4.80.8 script failed, exit status 255
    *** Error code 1

    Stop in /usr/local/ports/emulators/linux_base-8.
    *** Error code 1

    Stop in /usr/local/ports/emulators/linux_base-8.

This is because ${ARCH} is overwritten to "i386" by Makefile,
and this overwritten ${ARCH} is passed to another make process
by the .MAKEFLAGS target in bsd.port.mk.
So, when the following part of Makefile is interpreted,

    .if (${ARCH} == "amd64")
    LATEST_LINK:=		${LATEST_LINK:C/linux/linux32/}
    ARCH=			i386
    FALLBACK_ELF_MIB=	kern.elf32.fallback_brand
    RPMFLAGS+=		--noscripts
    .else
    FALLBACK_ELF_MIB=	kern.fallback_elf_brand
    .endif

FALLBACK_ELF_MIB becomes to "kern.fallback_elf_brand"
instead of "kern.elf32.fallback_brand".

Fix: Use ${MACHINE_ARCH} instead of ${ARCH} in ".if" statement.