Rollup of 5 pull requests

[Dylan-DPC-zz]

Successful merges:

• Document unsafe blocks in core::{cell, str, sync} #66564 (Document unsafe blocks in core::{cell, str, sync})
• Implement Lift using interners instead of in_arena #67791 (Implement Lift using interners instead of in_arena)
• Fix CI for embedded ARM targets #68194 (Fix CI for embedded ARM targets)
• [self-profiler] Add example to -Z help to turn on query key recording #68278 ([self-profiler] Add example to -Z help to turn on query key recording)
• Allow added string.insert benchmarks to compile #68300 (Allow added string.insert benchmarks to compile)

Failed merges:

r? @ghost

[Dylan-DPC-zz]

@bors r+ p=5 rollup=never

[bors]

📌 Commit 8c03d75 has been approved by Dylan-DPC

[rust-highfive]

Your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2020-01-17T12:34:57.1902979Z ========================== Starting Command Output ===========================
2020-01-17T12:34:57.1904845Z [command]/bin/bash --noprofile --norc /home/vsts/work/_temp/ede12ae4-65c8-438d-ae33-3460122b02d4.sh
2020-01-17T12:34:57.1904886Z 
2020-01-17T12:34:57.1908057Z ##[section]Finishing: Disable git automatic line ending conversion
2020-01-17T12:34:57.1914716Z ##[section]Starting: Checkout rust-lang/rust@refs/pull/68310/merge to s
2020-01-17T12:34:57.1916918Z Task         : Get sources
2020-01-17T12:34:57.1916952Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.
2020-01-17T12:34:57.1917033Z Version      : 1.0.0
2020-01-17T12:34:57.1917066Z Author       : Microsoft
---
2020-01-17T12:34:58.2154941Z ##[command]git remote add origin https://github.com/rust-lang/rust
2020-01-17T12:34:58.2188528Z ##[command]git config gc.auto 0
2020-01-17T12:34:58.2194396Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2020-01-17T12:34:58.2199213Z ##[command]git config --get-all http.proxy
2020-01-17T12:34:58.2214788Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/68310/merge:refs/remotes/pull/68310/merge

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