In `NCM::Component::spma`, `$self->prefix()` returns `/software/components/spma`, which is fine.  In `NCM::Component::spma::ips`, `$self->prefix()` returns `/software/components/ips` which is not what I want.  I therefore needed `CMP_TREE` in my `spma::ips` module, so also left it in the `spma` module to be consistent.

I suppose I could override the `prefix` subroutine in `call_entry_point` before invoking the final `Configure`?