Adapt https://github.com/aya-rs/aya/commit/3d463a3 and subsequent work
to the template. This has worked very well for us in the main project,
and our users should get the same hotness.
Note that xtask is still used for running, as it is in the main project.
Add a new command to build ebpf and userspace programs without running.
```
cargo xtask build
```
Co-authored-by: Michal Rostecki <vadorovsky@protonmail.com>
The default log level of env_logger is `error`. We are using `info!` in
the template, so let's suggest running the example with `RUST_LOG=info`.
Signed-off-by: Michal Rostecki <vadorovsky@gmail.com>