scripts: don't set LD_PRELOAD with static companion libraries

When cpmpanion libraries are built statically, it is useless to set
LD_PRELOAD. Worse, it might break the build in some corner cases.

# Compute IA-64-specific values

CT_DoArchTupleValues() {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="${CT_ARCH}"

}