Rollup of 11 pull requests

[eddyb]

• Successful merges: rustbuild: Add support for compiling Cargo  #39917, librustc error_reporting.rs cleanup. #39977, Add missing urls and examples for Condvar docs #40033, Add compile fail test for unboxed_closures feature #40047, Replace ./configure with config.toml in README.md and CONTRIBUTING.md #40056, Fix nightly-only experimental API display #40057, Made no_stack_check a stable_removed attribute #40110, Example for how to provide stdin using std::process::Command #40122, Remove unnecessary "for" #40124, Add missing docs and examples for fmt::Write #40126, Make lifetime elision docs clearer #40131
• Failed merges: Add compile fail test for SIMD #40101

[rust-highfive]

r? @brson

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[eddyb]

@bors r+ p=10

[bors]

📌 Commit ac50a57 has been approved by eddyb

[eddyb]

@bors r-