scripts/functions: cvs retrieval first tries the mirror for tarballs

The cvs download helper looks for the local tarballs dir to see if it
can find a pre-downloaded tarball, and if it does not find it, does
the actual fetch to upstream via cvs.

In the process, it does not even try to get a tarball from the local
mirror, which can be useful if the mirror has been pre-populated
manually (or with a previously downloaded tree).

Fake a tarball get with the standard tarball-download helper, but
without specifying any upstream URL, which makes the helper directly
try the LAN mirror.

Of course, if no mirror is specified, no URL wil be available, and
the standard cvs retrieval will kick in.

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

 # Compute powerpc-specific values

 CT_DoArchTupleValues () {

     # The architecture part of the tuple, override only for 64-bit

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

         CT_TARGET_ARCH="powerpc64"

     fi

     # Add spe in the tuple if needed

     case "${CT_LIBC},${CT_ARCH_POWERPC_SPE}" in

         glibc,|eglibc,)   CT_TARGET_SYS=gnu;;

         glibc,y|eglibc,y) CT_TARGET_SYS=gnuspe;;

     esac

     # Add extra flags for SPE if needed

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

         CT_ARCH_TARGET_CFLAGS="-mabi=spe -mspe"

         CT_ARCH_CC_CORE_EXTRA_CONFIG="--enable-e500_double"

         CT_ARCH_CC_EXTRA_CONFIG="--enable-e500_double"

     fi

 }