Add a global verbose option

Debugging #2079 i realized that we currently require `RUST_LOG=debug` for users to debug issues like missing inclusions. I added a global counting `-v` flag.

We currently use `-v` to configure cargo verbosity level. For simplicity, it now configures both at the same time. Fine-grained control is still possible by setting `RUST_LOG`.

The levels:
* Default: Show build information and `cargo build` output.
* `-v`: Use `cargo build -v`.
* `-vv`: Show debug logging and use `cargo build -vv`.
* `-vvv`: Show trace logging.

This can be extended to support a quiet option.