Make use of inspect and wave tools conditional.

When using bcp, the inspect tool is normally not copied, and
wave tool is not copied unless wave library is requested. However,
Jamroot unconditionally refers to those projects via use-project.
It's not entirely clear why it does so, and the commits that add
reference have no rationale.

This commit takes the safe route of guarding use of these projects
with the check for their presence.