rust: xdppass: Use libbpf-cargo build script

[danobi]

Build script is better than cargo plugin b/c you can't forget to run the
skeleton generation step.

[danobi]

cc @chenhengqi

[chenhengqi]

It looks good.

One small question, the current implementation use relative path rather than CARGO_MANIFEST_DIR, does it works in both workspace dir and crate dir?

[danobi]

One small question, the current implementation use relative path rather than CARGO_MANIFEST_DIR, does it works in both workspace dir and crate dir?

It should work. https://doc.rust-lang.org/cargo/reference/build-scripts.html says:

In addition to environment variables, the build script’s current directory is the source directory of the build script’s package.

[danobi]

@anakryiko ping