D lang compilers have an option -release (or similar) which turns off
asserts, contracts, and other runtime type checking. This patch wires
that up to the b_ndebug flag.
Fixes#7082
The library from which we extract should have multiple sources
from which we choose a strict subset otherwise we're testing almost the
same case extracting all the objects.
This exposes a bug in how we were doing extract checking for unity
builds.