configure: portability fixes - take 2

It is useful to sometime run on a strictly POSIX-compliant
shell... :-/

And it is sometime interesting to refresh Q-patches before
finishing the series... :-(

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Compute sparc-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

    if [ "${CT_ARCH_64}" = "y" ]; then

        CT_TARGET_ARCH="${CT_ARCH}64"

    fi

}