Add test for issue 4866

[gnzlbg]

This adds a test for issue #4866. Fixing that issue should fix this test.

The problem in a nutshell is that when doing cargo build the features of dev dependencies and disabled platform-specific dependencies get unified/activated/pulled-in. See the issue for more details.

This test covers dev-dependencies and an impossible platform-specific dependency.

This test should be enhanced with a platform-specific dependency that pulls in some feature in some platform but not others.

[rust-highfive]

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

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[alexcrichton]

Thanks! It's probably best to hold off on merging the test though?

[gnzlbg]

@alexcrichton Yes I think so, I am going to try to fix this today, but the second part of this test fails or passes sporadically due to #5009 and I don't know how to work around that. Like I need to check the output of rustc for --cfgss for multiple crates, and the order of the crates is always different. Any hints would be welcomed.

[matklad]

Like I need to check the output of rustc for --cfgss for multiple crates, and the order of the crates is always different.

You can use multiple with_stderr_contains

[bors]

☔ The latest upstream changes (presumably #5063) made this pull request unmergeable. Please resolve the merge conflicts.

[alexcrichton]

I'm gonna close this for now as it's gone stale, but it can of course be resubmitted!