Minimalist Cross-Compiled Gentoo

#!/bin/sh
# vim: set ts=4 sts=4 sw=4 et :

NAME=myrpi
CONFIGROOT=configroot
ARCH=arm
ELIBC=glibc
PROFILE=embedded
CTARGET=armv6j-hardfloat-linux-gnueabi
#UNSTABLE=1

# =========================================================================== #

if [ $(id -u) -ne 0 ]; then
    echo "$(basename "$0") must be run as root!" &>2
    exit 1
fi

set -e

export ROOT="${TMPDIR:-${TEMP:-${TMP:-/var/tmp}}}/${NAME}"
export EMERGE_DEFAULT_OPTS="--quiet --quiet-build --quiet-fail --usepkg \
    --nospinner --misspell-suggestions=n"
export PORTAGE_CONFIGROOT="${ROOT}"

test -d "${ROOT}"/etc/portage || mkdir -p "${ROOT}"/etc/portage

if [ -n "${CONFIGROOT}" ]; then
    cp -r "${CONFIGROOT}"/. "${ROOT}"/etc/portage/
fi

test -d "${ROOT}"/etc/portage/profile || mkdir -p "${ROOT}"/etc/portage/profile

cat > "${ROOT}"/etc/portage/profile/make.defaults <<EOF
ARCH=${ARCH}
ELIBC=${ELIBC}
ACCEPT_KEYWORDS="${ARCH}${UNSTABLE:+ ~${ARCH}}"
FEATURES="-news"
USE="${ARCH} bindist minimal"
EOF

cat > "${ROOT}"/etc/portage/make.conf <<EOF
CFLAGS="\${CFLAGS} --sysroot=${ROOT}"
CXXFLAGS="\${CFLAGS}"
LDFLAGS="\${LDFLAGS} --sysroot=${ROOT} -Wl,--sysroot=${ROOT} -L=/usr/lib -Wl,-verbose"
FEATURES="buildpkg"
USE="ipv6"
EOF

portdir=$(portageq envvar PORTDIR)
ln -snf "${portdir}"/profiles/${PROFILE:-embedded} \
    "${ROOT}"/etc/portage/make.profile

CFLAGS= LDFLAGS= FEATURES='-buildpkg' ${CTARGET}-emerge --oneshot --noreplace \
    virtual/libc virtual/os-headers

export SYSROOT="${ROOT}"

${CTARGET}-emerge --noreplace --changed-use \
    app-shells/bash \
    app-arch/bzip2 \
    sys-apps/coreutils \
    sys-apps/file \
    sys-apps/findutils \
    sys-apps/gawk \
    sys-apps/grep \
    app-arch/gzip \
    sys-apps/kbd \
    sys-apps/kmod \
    sys-apps/less \
    sys-apps/openrc \
    sys-apps/net-tools \
    sys-process/procps \
    sys-apps/sed \
    sys-apps/shadow