check-exercises: Silence non-warning output in DENYWARNINGS mode
check-exercises: Silence non-warning output in DENYWARNINGS mode

In DENYWARNINGS I just want to see all the warnings; I don't care about
whether the tests actually pass or what I'm compiling or downloading.

sacherjj/rust,petertseng/exercism-rust,sacherjj/rust,exercism/xrust,exercism/xrust,petertseng/exercism-rust,petertseng/exercism-rust,sacherjj/rust