Add config option and cli arg for skip-llvm-rebuild

[Walther]

Fixes#65612.

First time contributing, please let me know if there's anything I need to tweak 🙂 ❤️

[rust-highfive]

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

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[rust-highfive]

The job x86_64-gnu-llvm-6.0 of 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.

2019-10-26T15:31:29.8394278Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-10-26T15:31:29.8589462Z ##[command]git config gc.auto 0
2019-10-26T15:31:29.8651565Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-10-26T15:31:29.8706291Z ##[command]git config --get-all http.proxy
2019-10-26T15:31:29.8826978Z ##[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/65848/merge:refs/remotes/pull/65848/merge
---
2019-10-26T15:37:48.9541542Z Compiling serde_json v1.0.40
2019-10-26T15:37:50.5816216Z Compiling tidy v0.1.0 (/checkout/src/tools/tidy)
2019-10-26T15:38:01.3701437Z Finished release [optimized] target(s) in 1m 23s
2019-10-26T15:38:01.3772259Z tidy check
2019-10-26T15:38:01.7770035Z tidy error: /checkout/src/bootstrap/bootstrap.py:827: line longer than 100 chars
2019-10-26T15:38:03.5427586Z Found 484 error codes
2019-10-26T15:38:03.5427656Z Found 0 error codes with no tests
2019-10-26T15:38:03.5427697Z Done!
2019-10-26T15:38:03.5427756Z some tidy checks failed
2019-10-26T15:38:03.5427756Z some tidy checks failed
2019-10-26T15:38:03.5427779Z 2019-10-26T15:38:03.5427799Z 2019-10-26T15:38:03.5428496Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "--no-vendor"
2019-10-26T15:38:03.5428596Z 2019-10-26T15:38:03.5428617Z 2019-10-26T15:38:03.5428669Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
2019-10-26T15:38:03.5428707Z Build completed unsuccessfully in 0:01:27
2019-10-26T15:38:03.5428707Z Build completed unsuccessfully in 0:01:27
2019-10-26T15:38:03.5473041Z == clock drift check ==
2019-10-26T15:38:03.5485857Z local time: Sat Oct 26 15:38:03 UTC 2019
2019-10-26T15:38:03.6959967Z network time: Sat, 26 Oct 2019 15:38:03 GMT
2019-10-26T15:38:03.6968758Z == end clock drift check ==
2019-10-26T15:38:05.0970795Z 2019-10-26T15:38:05.1043064Z ##[error]Bash exited with code '1'.
2019-10-26T15:38:05.1074805Z ##[section]Starting: Checkout
2019-10-26T15:38:05.1076799Z ==============================================================================
2019-10-26T15:38:05.1076852Z Task : Get sources
2019-10-26T15:38:05.1076912Z Description : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[Walther]

I'm not sure if adding the pub skip_llvm_rebuild: bool into the config is a great thing, as the Rust side of the build will not use that config option anywhere. On the other hand, tidy check will fail without it, as it will fail to parse the unknown property in the config.toml file.

[alexcrichton]

Thanks for the PR! I think I may be missing something though? It looks like this adds configuration for skipping an LLVM rebuild but doesn't actually end up reading it when building LLVM?

Also cc @varkor who requested these changes

[Walther]

Ah, it's not enough to skip the submodule in bootstrap.py https://github.com/rust-lang/rust/pull/65848/files#diff-3e203f016947a52e3f1fad3967027e7eR734-R740 - sorry, I'll take a new look at where else it needs to be skipped 👍

[JohnCSimon]

Ping from triage:
@Walther can you please post your status on this pr?
cc: @alexcrichton@varkor

Thank you!

[Walther]

I have a simple question - at src/bootstrap/config.rs line 388 ish, i'd love to add config.skip_llvm_rebuild to be set from the bootstrap.py too like some other settings are, as i did the handling of CLI args & TOML setting already there. Should I set a new capitalized env var for it, or should i plop it within RUSTFLAGS or some such in build_bootstrap(), or something completely different? I just need the already-resolved self.skip_llvm_rebuild in RustBuild() in Python/bootstrap side to be visible in Rust side too.

In addition to what's visible in the PR, I already locally added the lines necessary to actually skip the LLVM build in native.rs

if builder.config.skip_llvm_rebuild{
builder.info("Skipping LLVM rebuild");return build_llvm_config
}

[alexcrichton]

I think in general it's fine to only update config.rs, I suspect that bootstrap.py doesn't really need any changes for this. Inside of native.rs yeah I think you'd basically have that block which would skip any amount of LLVM rebuilding.

[JohnCSimon]

Ping from triage:
@Walther - can you address the comments from @alexcrichton so this can be moved forward?

Thank you!

[Walther]

Sorry, I've been fairly busy! I hope I can get back at this next weekend or so. If not, and if someone wants to quickly fix this instead, that's okay too. There's always more issues to help with :)

[joelpalmer]

Ping from Triage: Any update @Walther?

[JohnCSimon]

Ping from triage:
@Walther - can you please post your status for this PR?

Thank you.

[JohnCSimon]

Ping from triage:
@Walther - Unfortunately this PR has sat idle for far too long, and I am going to close it as inactive. Please reopen it when you have the time to make the necessary changes or find help to move this forward.
Please do not push to the PR while it is closed as that prevents it from being reopened.
Thank you for your efforts!