archbuild: Avoid unnecessary use of basename(1)

base_packages=(base base-devel sudo)

cmd="$(basename "${0%-build}")"

if [[ "${cmd%-*}" == 'multilib' ]]; then

	repo="${cmd}"

cmd="${0##*/}"

if [[ "${cmd%%-*}" == 'multilib' ]]; then

	repo="${cmd%-build}"

	arch='x86_64'

	base_packages+=(multilib-devel)

else

	repo=${cmd%-*}

	arch=${cmd##*-}

	tag="${cmd%-build}"

	repo=${tag%-*}

	arch=${tag##*-}

fi

chroots='/var/tmp/archbuild'

clean_first=false

usage() {

	echo "usage $(basename "$0")"

	echo "usage $cmd"

	echo '    -c         Recreate the chroot before building'

	echo '    -r <dir>   Create chroots in this directory'

	exit 1