`rust+CARGO` build should assume output? about lib

[idelvall]

Hi Adam, thanks!
The original implementation worked that that way, but we soon realized that the target cache grew significantly even with cargo-sweep installed (more than 10GB in some cases), so we were not adding significant runtime overhead by copying all the files (most of then not needed), we were also significantly polluting the build layer cache.
Another thing I considered was instead of adding an "--output" option add a "--save-artifact" one, so no need for redundant information, but I think this is cleaner

[adamgordonbell]

Makes sense.
I'm just talking about a default. So you could still use the output flag, but if you didn't, you wouldn't be surprised that you ended up with no files. Keep in mind the user of the UDC has no idea how it works internally and probably just wants the output of their cargo call.

Maybe its too early to say. If other people use it and get tripped up by this it might make sense to consider.

[idelvall]

The output is an ARG in the UDC, so it's not an implementation detail, but even if a user ignores what it does,
I think it's better to force them to read the API documentation by don't outputting anything, rather than giving them the output without being aware of the side effects of that as the cache grows.
At least that is what I would prefer, but yes, let's wait to see how people react to all of this.

Thanks Adam!