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}"

 }