[cargo-wdk] Ensure cargo-wdk respect other forms of target tuple/architecture override

[krishnakumar4a4]

The first cut of cargo-wdk only respects the --target-arch CLI argument to build the driver to specific CPU architecture (only Amd64 & Arm64 supported as of now).

If the driver developer attempts to override target through a config.toml or through an env variable, the behaviour is undetermined & unsupported as of now.

This issue is opened to track and address the same.