CI: spurious hang on x86_64-msvc-1 during rustc_macros compilation

[matthiaskrgr]

Sometimes the build hangs there.

Wed, 26 Jan 2022 05:45:45 GMT running 0 tests
Wed, 26 Jan 2022 05:45:45 GMT
Wed, 26 Jan 2022 05:45:45 GMT test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
Wed, 26 Jan 2022 05:45:45 GMT
Wed, 26 Jan 2022 05:45:45 GMT    Doc-tests rustc_log
Wed, 26 Jan 2022 05:45:45 GMT
Wed, 26 Jan 2022 05:45:45 GMT running 1 test
Wed, 26 Jan 2022 05:45:45 GMT test src\lib.rs - (line 15) ... ok
Wed, 26 Jan 2022 05:45:45 GMT
Wed, 26 Jan 2022 05:45:45 GMT test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.63s
Wed, 26 Jan 2022 05:45:45 GMT
Wed, 26 Jan 2022 05:45:45 GMT 	finished in 1.616 seconds
Wed, 26 Jan 2022 05:45:45 GMT [TIMING] Crate { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-msvc", file: None } }, target: TargetSelection { triple: "x86_64-pc-windows-msvc", file: None }, mode: Rustc, test_kind: Test, krate: "rustc_log" } -- 1.618
Wed, 26 Jan 2022 05:45:45 GMT [TIMING] CrateLibrustc { compiler: Compiler { stage: 2, host: TargetSelection { triple: "x86_64-pc-windows-msvc", file: None } }, target: TargetSelection { triple: "x86_64-pc-windows-msvc", file: None }, test_kind: Test, krate: "rustc_log" } -- 0.000
Wed, 26 Jan 2022 05:45:45 GMT Set({"compiler\\rustc_macros"}) not skipped for "bootstrap::test::CrateLibrustc" -- not in ["src/test/ui", "src/tools/linkchecker"]
Wed, 26 Jan 2022 05:45:45 GMT Testing rustc_macros stage1 (x86_64-pc-windows-msvc -> x86_64-pc-windows-msvc)
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] build_script_build test:false 0.695
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] unicode_xid test:false 0.150
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] build_script_build test:false 0.592
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] proc_macro2 test:false 1.727
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] quote test:false 0.726
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] syn test:false 15.990
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] synstructure test:false 1.921
Wed, 26 Jan 2022 05:45:46 GMT [RUSTC-TIMING] rustc_macros test:false 4.037
Wed, 26 Jan 2022 05:45:46 GMT    Compiling rustc_macros v0.1.0 (D:\a\rust\rust\compiler\rustc_macros)
Wed, 26 Jan 2022 09:11:12 GMT Error: The operation was canceled.

https://github.com/rust-lang-ci/rust/runs/4947161125?check_suite_focus=true#step:26:25990

[matthiaskrgr]

@rustbot modify labels: +T-infra +A-spurious +O-windows +O-windows-msvc

[ehuss]

One possibility could be something like #92829. That builder has assertions enabled.

[ehuss]

Also happening with i686-msvc-1, so not specific to x86_64.

#92740 (comment)