Bugzilla Bug 210039

here is the current code:
    if use amd64 || use ppc64 || use ia64 || use s390; then
        myconf="${myconf} --enable-64bit"
    else
        myconf=""
    fi

problems:
 - s390 is not a 64bit arch ... s390x is ... but s390x is not a KEYWORD.  s390
and s390x both use the s390 KEYWORD.
 - 64bit mips is ignored

if the build system is so terrible it cannot do the 64bit detection itself,
then use the toolchain to produce an object and run file on it:
echo > "${T}"/test.c
$(tc-getCC) -c "${T}"/test.c -o "${T}"/test.o
case $(file "${T}"/test.o) in
    *64-bit*) myconf="${myconf} --enable-64bit"
    *32-bit*) ;;
    *) die "FAIL";;
esac

Added, thanks