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 pefile module is a CI dependency now, so we can use that instead
of objdump/dumpbin which greatly simplifies the test. Of course, this
module is also cross-platform so it will work if we add cross-win32 CI
at some point.