Stop printing rustc command line if normally errored

[Mark-Simulacrum]

We used to print a wall of text especially in larger projects like the
compiler, now we print a much smaller message. It's not generally useful
to know the full compiler command anyway.

Not completely sure this is the best place to have this, but seems to work in local testing.

[rust-highfive]

r? @alexcrichton

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[dwijnand]

Might be nicer to keep using ExitStatus here, rather than a raw i32.

[Mark-Simulacrum]

AFAICT there's no way to construct one

[dwijnand]

🤦‍♂️ sorry

[dwijnand]

Thinking along the lines of @alexcrichton's comment in #5683 (the arch-rival to this PR), perhaps rather than do an exit code conditional thing the verbose output could be gated on -v (or -vv).

[Mark-Simulacrum]

That does sound like a mostly better idea -- I'll update this PR (and fix tests) soon.

[alexcrichton]

Hm the intention for Cargo has always been that if -v is passed we print the full rustc command line, and then in practice it ends up being passed very rarely. Something is different about rustbuild though (I forget how) where something is on by default to display more verbose errors. I'd prefer to solve that for rustbuild and keep the current interface of -v means "print the full command line"

[Mark-Simulacrum]

Hm yes looks like this is actually a rustbuild bug. I'll look into it.