test-suite: apply cleanup pass

Remove all non-modifiable items (target tuple, gcc version, toolchain path...)
Makefile syntax ( use $(...) instead of ${...} )
Update doc
Space-damage cleanups

# Compute Alpha-specific values

CT_DoArchTupleValues () {

    # The architecture part of the tuple:

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

}