scripts: simplify and fix the toolchain config script

The script that is installed, and which sole purpose is to dump
the .config that was used to build the toolchain, is pure insanity.

Let's make it much, much more simpler...

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

 # Compute Alpha-specific values

 CT_DoArchTupleValues () {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}${CT_ARCH_ALPHA_VARIANT}"

 }