Multi-Arch Directory Structure

[hone]

Currently when using cargo libcnb package, it outputs the resulting buildpack into target/buildpack. This works great in the default (single arch) use case, but if you want to support multiple archs they will clobber each other. What if we put buildpack inside an arch directory? For instance:

target/buildpack/<mode>/<name> -> target/buildpack/<arch>/<mode>/<name>

Another alternative but could just be a good addition would be an --out-dir like cargo build (though this is unstable atm).

[jasonschroeder-sfdc]

There may be patterns to follow from here... rust-lang/cargo#8875
It reminds me of macOS universal binaries, where one file supports multi-arch.

I think --out-dir is more flexible (and could be used to implement the first option)

[Malax]

target/buildpack/<mode>/<name> -> target/buildpack/<arch>/<mode>/<name>

Is exactly what Cargo does in the regular target directory. I think keeping parity with Cargo itself is worthwhile, especially when we're using the same output directory. We did this for the command line arguments as well to keep the surprise factor low.