Improved error reporting when target sysroot is missing.

[shiver]

Attempts to resolve#37131.
This is my first pull request on rust, so I would greatly appreciate any feedback you have on this.

Thanks!

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @nrc (or someone else) soon.

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[nrc]

r? @alexcrichton

[bors]

☔ The latest upstream changes (presumably #37350) made this pull request unmergeable. Please resolve the merge conflicts.

[brson]

Thanks @shiver!

This looks good to me, with the exception that it needs a test.

I'd say the best way to do it is to add a test to src/test/compile-fail that is annotated with

// compile-flags: --target=s390x-unknown-linux-gnu
// ignore s390x

You can crib off other tests in that directory for details.

[shiver]

Excellent! Thanks for the feedback.

I'll hopefully push the test in the next day or two.

[alexcrichton]

This should be --target={}, right?

[shiver]

Sorry about that.
Definitely a bug. I was having some issues with the tests, sometimes all passing (possibly because I wasn't recompiling rustc correctly), so I didn't pick that up.

Hopefully the latest commit addresses this.

[alexcrichton]

Perhaps this could be "may not be installed" as it may actually be and we could be error'ing for some other reason?

[shiver]

Yeah, that seems like a better idea.
I have changed the message to read "the <target> target may not be installed".

[alexcrichton]

Thanks! Want to squash the commits?

[shiver]

Hopefully squashed in the correct manner. Let me know if you see any issues though!

[alexcrichton]

@bors: r+

Thanks!

[bors]

📌 Commit 66de87f has been approved by alexcrichton

[bors]

⌛ Testing commit 66de87f with merge c356537...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: alexcrichton
Pushing c356537 to master...