Rollup of 6 pull requests

[frewsxcv]

• Successful merges: rustbuild: Add support for compiling Cargo  #39917, travis: Fuchsia builder #39918, librustc error_reporting.rs cleanup. #39977, Add compile fail test for unboxed_closures feature #40047, Fix nightly-only experimental API display #40057, Fix a typo #40078
• Failed merges:

[frewsxcv]

@bors r+ p=10

[rust-highfive]

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

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[bors]

📌 Commit ea158e3 has been approved by frewsxcv

[bors]

⌛ Testing commit ea158e3 with merge 4335b02...

[bors]

💔 Test failed - status-travis