Add Dub.overrideSearchPath to define a single and only path that is searched for packages.
Add support for execution result callbacks in the build generator.
Add a basic dustmite command.
Avoid scanning for local packages for "dub dustmite --test-package".
Avoid copying compiler output files and copy *all* dependencies for "dub dustmite".
Fix matching linker/program results in dustmite mode and output match status messages.
Only force dustmite match when an explicit failing exit code was requested.
Dustmite: Force a match when a command failed, but the output regex matched.