`@bors try` should not deny warnings

[lcnr]

I've had multiple try builds fail because of an unused import. This is annoying and seems unnecessary.

We should disable deny-warnings in try builds.

[matthiaskrgr]

I think it will be very confusing when suddenly ci will fail although the try jobs passed previously, but maybe we can have something like try-job-light with a separate command?

[lcnr]

CI already fails in a lot of cases where explicit @bors try builds succeed. Try builds do not check clippy or run UI tests.

[matthiaskrgr]

ah this is about just a @bors try without any try-job: x86_64-gnu-distcheck-esque stuff 👍
makes sense then :)

[jieyouxu]

cc @rust-lang/infra-bors

[Kobzol]

@lcnr do you want this for any custom try build (where you select the CI job executed), or only for the default try jobs that are used for perf. runs and crater?

[lcnr]

I don't care 😅 I guess let's only do it for default try jobs and if people get annoyed by other ones, fix it then

[compiler-errors]

I think default try builds could ignore warnings, since we primarily use them to generate artifacts. CI job ones are generally also used to validate things pass CI 😸